ACTIVE AIR SAMPLING FOR CONTAMINANTS IN THE WORKPLACE

ACTIVE AIR SAMPLING FOR CONTAMINANTS IN THE WORKPLACE
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ACTIVE SAMPLING DEFINED
The collection of airborne contaminants using a mechanical device such as a pump to draw the air/contaminant mixture into or through the sampling device such as a sorbent tube, filter, impinger, or sample bag. Let’s begin by defining active sampling. Active sampling is the collection….

THREE KEY COMPONENTS FOR ALL ACTIVE SAMPLING
A sampling pump Something to pull or push air A calibrator (flowmeter) Something to indicate how much air has been pulled or pushed The sampling media Something to pull or push the air through or into for analysis Regardless of the target compound that you are trying to collect, active air sampling will involve three key components in your sampling train. Read slide. You will need to consult a published sampling and analytical method to determine: -The flow rate of the sampling pump and -The particular sampling media to use for specific air contaminants.

U.S. GOVERNMENT METHODS SAMPLING IN THE WORKPLACE
National Institute for Occupational Safety and Health (NIOSH) Occupational Safety and Health Administration (OSHA) In the U.S., there are (2) government agencies that publish method manuals for air sampling in the workplace: The National Institute for Occupational Safety and Health (NIOSH) And The Occupational Safety and health Administration (OSHA).

NOTE ON SAMPLING METHODS
OSHA does not mandate the sampling method to be used for compliance. The employer has the obligation of selecting a method that meets the accuracy/precision requirements of the standard i.e. ± 25% of the true value. NIOSH or OSHA methods are typically used in compliance sampling. Note that OSHA does not mandate the sampling method to be used for compliance purposes. -YOU (as a representative of the employer) have an obligation of selecting a method that you can legally defend. -Methods should provide a result within plus or minus 25% of the true value. -NIOSH or OSHA methods are typically used, but other methods can be used if you have data to prove their reliability.

WEBSITES FOR GOV’T AGENCY METHODS
NIOSH Methods OSHA Methods html Both the NIOSH and OSHA Methods posted on the internet at the URLs shown on the slide. These are valuable sites that you will access frequently if you conduct regular air sampling. Be sure to bookmark these websites.

EXAMPLE: NIOSH METHOD Here is an example of a NIOSH Method.
On page 1 of the method, you can view all the critical details related to sample collection. On the top of this page, various exposure limits and synonyms are listed for the target compound. In the left hand column, you can see all the critical sampling details including sampling media, flow range, min/max air volume, and sample stability information. The right-hand column provides information on analysis equipment and measurement range. .

EXAMPLE: OSHA METHOD Here is an example of an OSHA sampling and analytical method. Since OSHA is a compliance agency, their methods contain a lot more detail for analysis and are typically pages in length. Like with the NIOSH methods, page 1 of the OSHA methods will provide the critical information that you need to collect the sample. On this page, you can read details on the exposure limits, sampling media and the general collection procedure including flow rate, sample time, quantitation limits, and standard error. (Later pages) in the OSHA methods provide valuable information on method history, toxic effects and typical workplaces with exposures to the target compound.

HELP FROM SKC: SAMPLING GUIDE IN SKC CATALOG
Lists all regulated chemicals Includes: Agency Method Number Sampling Details such as Flow Rate, Time, Volume Analytical method Sample collection media and catalog number SKC provides a sampling guide in our catalog and on our website with a summary of the sampling details from NIOSH and OSHA methods. We also have a sampling guide APP for your mobile device. The SKC Sampling Guide is a valuable reference to help you choose a sampling method and to select the proper collection media and pump flow rate to meet the requirements. The SKC Sampling Guide is used by health and safety professionals around the world.

SKC AIR SAMPLING GUIDE SKC Chemical Fact Files @ www.skcinc.com
Here you can see a page from the SKC Sampling Guide. The guide lists all the available NIOSH/OSHA methods for the contaminant of interest along with the exposure limit, sampling rate, sampling time for analytical reasons, air volume, and analytical method. The last column indicates the collection media and the page number in the SKC catalog. Note also the listing for the SKC Chemical Fact File in the sampling guide. SKC Chemical Fact Files are one-page summaries of the government agency methods that provide details on creating a sampling train and on the critical sampling parameters. Chemical Fact Files are available for free download on the SKC website. Simply click on the Training Hot Button or click on Sampling Help at SKC Chemical Fact Click Training or Sampling Help

TYPES OF ACTIVE SAMPLES FOR VARIOUS EXPOSURE PERIODS
Integrated samples-Contaminants are collected and concentrated over a period of time to obtain average exposure levels during the entire sampling period Grab samples-Contaminants are collected into a device over a short interval of a few seconds or minutes to represent exposures at a given point in time. Let’s now look at the types of active samples used to evaluate various exposure periods. With INTEGRATED samples, contaminants are collected and concentrated over a period of time to obtain AVERAGE exposure levels. Alternatively, with GRAB samples, contaminants are collected over a short interval to determine peak levels or exposures at a given point in time.

SAMPLING PUMPS: FLOWRATE OPTIONS
GASES AND VAPORS are sampled at low flow rates to allow effective adsorption to occur onto the sorbent material. PARTICULATES are sampled at high flow rates so that airborne particles can be effectively trapped onto the filter material. When you look at the SKC catalog, you will see a number of different sampling pumps with various flowrate options. Here’s some tips on choosing a pump for various applications. -Low flow pumps in industrial hygiene are those that sample at flow rates less than 1 Liter/min. Low flow rates are used to sample gases and vapors as they allow for effective adsorption onto the sorbent material. Higher flow rates will cause the vapors to blast through the media with little adsorption onto the sorbent material. -On the other hand, high flow pumps are used to sample particulates. Pumps with flow rates greater than 1 L/min allow airborne particulate matter to be captured and retained onto the filter. Many pumps can operate in both low and high flows. But some users prefer pumps with a dedicated high OR low flow range.

LOW FLOW PUMP: SKC POCKET PUMP
Flow range of ml/min Dedicated low flow pumps like the SKC Pocket Pump have less power requirements so they do not need a large battery. As a result, the pump is smaller and more lightweight. providing greater comfort and acceptance by those wearing the pumps throughout their workday. The SKC Pocket Pump has a flow range of ml/min.

HIGH FLOW PUMP WITH LOW FLOW OPTION
SKC AIRCHEK XR5000 Flow range of ml/min using either lithium-ion or alkaline batteries Higher flow pumps like the SKC XR50000 can achieve flows to 5 L/min and they offer a low flow option down to 5 ml/min with an adapter. These pumps provide the advantage of long run times and high backpressure capabilities through the use of supercharged lithium ion batteries. Like in your computer or cell phone, lithium ion batteries offer high power in a small package. Alkaline AA-batteries can also be used in the XR5000 pump if sampling in non-explosive atmospheres where intrinsic safety is not a consideration.

SAMPLING PUMPS: CONSIDERATIONS FOR USE
Constant Flow-Is there an internal mechanism to compensate for restrictions to flow? Electromagnetic Susceptibility-Is there shielding from RFI/EMI? Backpressure-What is the maximum pressure drop that the pump can handle? When choosing a sampling pump, you need to look at more than just the flow range however. You need to consider whether the pump: Is constant flow? In other words, can it compensate for any restrictions? Also does it flow fault and auto restart? You also need to consider whether the pump is shielded from electromagnetic susceptibility. Radio frequency interference from walkie talkies for example may cause the flowrate to rise or fall in unshielded pumps. Finally, ensure the pump handle the pressure drop. of typical sampling media particularly in dusty atmospheres?

PUMP CALIBRATORS Set and verify the flowrate of the pump to that required in the sampling method Should be done before and after every sample The average of the pre- and post- flowrates is used in calculations of air volume Next, let’s discuss pump calibration. Many new users are confused at the need for calibration when they just purchased a brand new pump. The term “CALIBRATION” as it relates to air sampling pumps means that you set and verify the flowrate of the pump to that required in the sampling method. Standards of good practice dictate that pump calibration should be done before/after every sample that you take. The average of the pre-and post-sample flowrates is used to calculate the air volume.

PUMP CALIBRATION: A CRITICAL MEASUREMENT
Purpose is to determine the volumetric flow rate that will pass through the sampling media during the time the sample is taken. The flowrate is used to calculate total air volume. FLOW RATE (ml/min or L/min) x SAMPLE TIME (min) =AIR VOLUME (ml or L) Pump calibration is a CRITICAL MEASUREMENT. The purpose is to determine the volumetric flow rate that will pass through the sampling media over the sample period. The flowrate is multiplied by the sample time to calculate air volume. The lab will determine the MASS of contaminant collected on the media, but if you don’t know the AIR VOLUME for the sample, the lab data is meaningless.

TYPES OF CALIBRATORS PRIMARY STANDARDS SECONDARY STANDARDS
involve the direct measurement of volume on the basis of the physical dimensions of an enclosed space which do not change over time. SECONDARY STANDARDS trace their calibration to primary standards and have shown to maintain their accuracy with reasonable handling and care in operation. Shown on this slide are the scientific definitions for the two general types of calibrators: Define primary standard. -Every user must have a a primary standard calibrator in your arsenal of equipment. Define secondary standard. -For ease in field use, most users will also want to have a secondary standard calibrator.

PRIMARY STANDARDS Soap bubble meters/Film flowmeters
Electronic bubble meters Electronic “near frictionless” piston meters Examples of primary standard calibrators include: Soap bubble meters otherwise known as film flowmeters Electronic bubble meters like the Buck calibrator or Gilibrator And Electronic near frictionless piston meters like the Defender.

SOAP FILM FLOWMETERS Pump pulls air through a glass tube with volumetric indications. The liquid film-a soap bubble-is interposed into the flow path. The air flow causes the bubble to move from one volume mark to another. The travel time is measured with a stopwatch By knowing the travel time and the tube volume, the flow rate can be calculated. In light of our current technology, soap Film Flowmeters or bubble meters seem like DINOSAURS. With these devices…. Despite the dinosaur technology, most hygienists still have some of these in their equipment cabinets as reference devices.

CALCULATION Question: If it took 128 seconds for the bubble
to travel a 500 ml volume, what is the flowrate? 500 ml X sec = ml/min 128 sec min After measuring the travel time of the bubble over a fixed volume, a calculation is done to determine the flowrate. Here’s an example for review: Read question. Well, if the bubble traveled 500 mls in 128 seconds, and there are 60 secs in a minute, the flowrate is calculated as ml/min. When doing this calculation, it is helpful to use the units to help you decide what goes in the numerator and denominator.

TECH TIPS ON CALIBRATION
It is not necessary for the flowrate to be the exact flow specified in the method. Just be sure you know exactly what it is. Take at least 3 flow measurements that agree within 5% and use the average of the readings as your flow rate measurement. If pre-and post-averages differ by more than 5%, your sample is called into question. Keep in mind the following technical tips on calibration. Read slide.

CALCULATIONS Given travel times for bubble: 128.2; 129.1;
128.7 seconds. Average time: seconds X 0.95 = X 1.05 = All times are within ± 5% range of acceptability Here’s an example calculation to determine if all your readings were within the +/- 5% range of acceptability. -After determining the travel times over a fixed volume for 3 bubbles, determine the average. -Then multiply the average travel time by 0.95 and 1.05. All readings should follow within this range. If not, repeat your measurements.

ELECTRONIC BUBBLE METERS
Work on the same principle as a manual film flowmeter Infrared sensors electronically time the bubble Microprocessor instantly calculates flow rate and displays it digitally Electronic bubble meters work on the same principle as a manual bubble flow meter. But instead of your eyeball and a stop watch, infrared sensors electronically time the bubble. Then instead of a calculator, a microprocessor instantly calculates the flow rate and displays it digitally. In the early morning hours, with a lot of pumps to calibrate, I would trust this electronic device over my tired eyes and slow reflexes any time.

NEAR-FRICTIONLESS PISTON METERS
The flow of the pump causes the piston inside a chamber to rise and fall. Photo-optic sensors sense the rise and fall of the piston. An electronic timer combine with a microprocessor to automatically measure travel time and calculate the flowrate. Near-frictionless piston meters are known as DRY calibrators since there is no soap bubble solution used. In this case, the flow of the pump causes the piston inside a chamber to rise and fall. Photo-optics sensors measure the rise and fall and electronics are used calculate and display the flowrate. These devices simplify the calibration process by eliminating the need for perfectly shaped bubbles for reliable readings.

NOTES ON ELECTRONIC CALIBRATORS
Both the electronic bubble meter and the piston meters use the volume of a cylinder to calculate the flow rate. Because of the fixed cell volume, these units are defined as primary standards by the manufacturer and are considered so by OSHA. They should be sent in for factory check annually or as needed. Note that both the electronic bubble meters and dry piston meters are considered primary standards. With both instruments, the fixed volume of a cylinder is used to determine the flow rate. These units should be sent in for annual factory recertification to maintain reliability of measurements.

Let your pumps run 5 minutes before calibration after removing them from the battery charger to let the flow stabilize. The pump must be calibrated with representative sample media in line. Use a clean set of media to collect the sample in the field after calibration. Here’s a couple more valuable technical tips on pump calibration. Read slide.

SORBENT TUBE SAMPLING TRAIN
On this slide, you can see a sorbent tube sampling train. Note that the tube is attached to the pump like its ready to be placed onto the worker. Then the open inlet end of the sample tube is connected to the pump calibrator to determine the flowrate. Once the pump is turned on, the bubble will begin to travel up the glass flowmeter. .

When available, use a calibration adapter to attach the sampler to the calibrator. Alternatively, use a calibration jar of a size to fit the sampler. Some sampling devices like cyclones can not be directly attached to the calibrator for flow measurement. When available, use a calibration adapter to the attach these sampling devices to the pump calibrator. Alternatively, you can use a calibration jar to enable flow measurement. In this case, the cyclone or other sampling device is placed within the jar, it is sealed to be airtight, and the inlet/outlet ports on the jar are then attached to the pump and the calibrator for flow measurements.

FILTER SAMPLING TRAIN WITH CALIBRATION ADAPTER
In this slide, you can see a sampling train with a filter cassette and the SKC aluminum cyclone in place. The aluminum cyclone has a handy calibration adapter that fits over the stem of the cyclone and allows for convenient attachment to the calibrator.

SECONDARY STANDARDS Rotameters Internal flow sensor
of an air sampling pump Wet Test Meter Dry Gas Meter Now let’s look at calibrators defined as secondary standards. Examples of secondary standards include: Read slide

ROTAMETERS Air passes through a vertical tube with
a ball or float inside The flow of air upward through the tube causes the ball to stabilize at a certain point The flow rate is determined by the position of the ball in relation to the scale on the tube Affected by both temperature and pressure With rotameters, air passes through a vertical tube with a ball or float inside. The flow of air causes the ball to stabilize at a certain point that corresponds to a flowrate indicated on the scale. An important consideration with rotameters is that they are affected by both temperature and atm pressure.

ROTAMETERS: CONSIDERATIONS FOR USE
If the rotameter was originally calibrated with one end open to the atmosphere (i.e. at atm. pressure) and you later use it for calibration in between the pump and media, the rotameter will indicate a lower flowrate. Given this information, please keep in mind the following consideration for use:

CALCULATION FOR ROTAMETERS
Qnew = Qntp [(760/Pnew) (Tnew/298)]0.5 Q. A rotameter was calibrated at NTP and measured a flow rate of 2 L/min. If the conditions changes to 30 C and 1.2 atmospheres, what should the new flow be? A. Qnew= 2 [760/(760 x 1.2)] [(273+30)/298]0.5 = L/min The easiest thing to do is calibrate your rotameter to a primary standard under the conditions of use. But if you must use a rotameter at a different temp and atm pressure, shown here is the formula. This formula is based on the scientific formula: P1V1/T1 = P2V2/T2 Keep in mind, when using this formula, temperature must be in degrees Kelvin which is Centigrade PLUS 273.

PROPER CALIBRATION Concentration in Air ENSURES ACCURATE
Air Volumes Measurement of exposure levels Flow Rate X Time=Air Volume Mass of contaminant/Air Volume= Proper calibration ensures accurate air volumes and measurements of exposure levels. Flow rate and sample time are used along with the mass of contaminant to determine concentration in air. Concentration in Air

SAMPLING MEDIA: ACTIVE SAMPLING OF GASES AND VAPORS
Now let’s discuss the final component of active sampling: the sample collection media. We’ll begin by reviewing sampling media for gases and vapors.

DEFINING GASES AND VAPORS
A substance is considered a GAS if this is its normal physical state at room temp (25o C) and one atm. (760 mm Hg) pressure (Example: Carbon monoxide) If the substance is a liquid at normal temp and pressure, then the gaseous component in equilibrium with its liquid (or solid) state is called a VAPOR. (Example: Benzene) For clarification purposes, we’ll begin by defining a gas vs a vapor. Read slide.

SOLID SORBENTS INTRODUCTION
Most widely used media for gases/vapors Consist of small granules or beads Adsorb the contaminant onto the surface Packed into tubes to collect various amounts and types of chemicals Solid sorbents including activated charcoal are the most widely used media for the collection of gases and vapors. These materials consist of small granules or beads of adsorbent material that ADsorb the contaminant onto the surface. The adsorbent material is packed into small glass tubes to collect various amounts and types of airborne chemicals.

SAMPLE COLLECTION WITH SORBENT TUBES
Most tubes have 2 sorbent sections. Breakthrough (sample loss) is indicated when contaminant levels on the backup section are ≥ 25% of the levels found on front sorbent section. Most sorbent tubes have 2 sorbent sections: a primary collection layer and a backup layer. Read slide on breakthrough Note also from this slide that tubes should be in a VERTICAL positioning during sampling. If placed horizontally, a small air gap may form as the sorbent falls away from the wall of the glass tube. Then the contaminant vapors will take the path of least resistance through this air gap and will not adsorb onto the collection media.

MORE ON SAMPLE BREAKTHROUGH
Causes High concentrations of target compound High concentrations of similar compounds High humidity High temperatures False Breakthrough Some chemicals may migrate from the front to the back sorbent layers upon storage. The method will specify freezer storage or the use of two separate tubes in these cases. Common causes of sample breakthrough include: Read slide. False indicators of breakthrough may occur if chemicals migrate from the front to the back sorbent layer upon storage. If this is a possibility, however, the method will typically specify the use of 2 separate tubes (rather than a single tube with 2 sections) OR the method will specify freezer storage of the sample after collection.

SOLID SORBENTS SPECIFIED IN SAMPLING METHODS
Trap and retain the contaminant even in the presence of other contaminants Allow desorption of the contaminant Have sufficient capacity to retain enough contaminant for analysis Will not cause a chemical change of the contaminant -Note that the sampling and analytical method will specify the type and amount of sorbent to use for specific target chemicals. -SKC manufactures sorbent tubes for nearly all published OSHA or NIOSH methods. -The sorbent specified in sampling methods will Read slide.

TYPES OF SORBENT MATERIAL: CARBON BASED SORBENTS
Activated charcoal-Most widely used solid sorbent suitable for collection of non-polar organic compounds including benzene, toluene, and xylene. Anasorb® 747-Beaded carbon material that can collect a variety of both nonpolar and polar organic compounds. Carbotrap® and Carbosieve® -High surface area; useful for very volatile compounds. SKC offers hundreds of sorbent tubes with different types of sorbent materials for published methods. Carbon based sorbents include: activated charcoal and Anasorb 747 from SKC and Carbotrap and Carbosieves sold by Supelco.

TYPES OF SORBENT MATERIAL: INORGANIC SORBENTS
Silica gel-Used to collect polar organic compounds such as alcohols, amines, and phenols. Silica gel is commonly used as a desiccant as it readily adsorbs water vapor. Alumina-Not widely used at this time. Specified in one OSHA partially validated method for an amine. Examples of inorganic sorbents include: Silica gel and alumina. Silica gel is used to collect some polar organic compounds such as alcohols, amines, and phenols. But alumina is not widely used at this time.

TYPES OF SORBENT MATERIAL: ORGANIC POLYMERS
Poropaks®, Chromosorbs®, XAD resins and Tenax®. These sorbents are used to collect a variety of specialty compounds. Chromosorbs and XAD-2 are specified in NIOSH and OSHA methods for pesticides. Tenax is specified in thermal desorption methods for (sub) ppb level VOC sampling. Sorbents made of organic polymers include Poropaks, Chromosorbs, XAD resins, and Tenax. They are used to collect a variety of specialty compounds. For example: -XAD resins are used for pesticides. -Tenax is used for low level VOC sampling followed by thermal desorption. We will discuss thermal desorption in more detail in the next few slides.

SORBENT TUBES FOR SOLVENT EXTRACTION
Sorbent tubes specified for workplace compliance sampling in the ppm range are designed for solvent extraction by the lab. The lab will break open the tube, pour the sorbent into vials, add a liquid solvent, and shake for a while so that the solvent extracts the contaminant from the solid adsorbent and into the liquid for GC analysis. Read slide.

SORBENT TUBES FOR THERMAL DESORPTION
Sorbent tubes specified for low level sampling in the ppb range are designed for thermal desorption by the lab. The lab will place the tube into the thermal desorber and apply heat and an inert gas to drive contaminant molecules from the adsorbent material to the detector of the GC. Provide lower detection limits. If instead, you need to do air sampling in the ppb range for environmental or other low level applications, specialty sorbent tubes designed for thermal desorption are typically used. In this case, sorbent is packed into open-ended stainless steel or glass tubes and it is thermally purged to ensure the sorbent is ultra clean. After sample collection, the lab will place….

TYPES OF SORBENT MATERIAL: MISC.
PUF Cartridges-used for semi-volatiles including PCBs and pesticides by ASTM or EPA methods. Not specified in any workplace methods. Other specialty sorbent materials include polyurethane foam cartridges. These so-called PUF tubes are used for the collection of semi-volaties including PCBs and pesticides following ASTM or EPA methods.

TYPES OF SORBENT TUBES: MISC.
Sorbent/Filter Combinations Filters capture or scrub out particulate phase; sorbents capture vapor phase. Specified in OSHA or NIOSH methods for pesticides, glycols, and hydrogen sulfide. Some recent OSHA / NIOSH methods specify tubes that contain both sorbents and small internal filters. The sorbent/filter combination tubes capture or scrub out particulate phase contaminants and simultaneously collect contaminants in the vapor phase. These sorbent/filter combination tubes are specified in OSHA or NIOSH methods for pesticides, glycols, and hydrogen sulfide. OVS H2S

TYPES OF SORBENT MATERIAL: WASHED OR COATED
Some chemicals are not effectively trapped by any solid sorbent without special preparation. Washing is done of silica gel to trap inorganic acids such as hydrochloric or hydrofluoric. Chemical coating is done on various sorbents to trap aldehydes, nitrogen dioxide, amines, and many more compounds. Some chemicals are not effectively trapped by any solid sorbent without special preparation or treatment. For example, silica gel must be washed multiple times to scrub out the inorganic contaminants so it can be used to collect inorganic acid gases such as HCl or HF. Chemical coating is done on various sorbents to trap common contaminants such as formaldehyde, nitrogen dioxide, amines, and many more.

SORBENT TUBE SAMPLING ADVANTAGES
Sample is integrated over the entire period of exposure. Published methods exist with extensive testing and documentation of reliability. Workplace compliance officers typically use this sampling method. Air flow is calibrated and measured. Backup layer indicates sample breakthrough. Sorbent tube sampling offers users many advantages.

IMPINGERS INTRODUCTION
Impingers are specially designed glass bottles that are filled with a collection liquid specified in the sampling and analytical method. Some sampling methods specify the use of impingers to collect target contaminants. Read slide.

NOTES ABOUT IMPINGERS In some cases, the impinger
nozzle is fritted or modified with thousands of small holes. This disperses the air and allows for better contact between the air sample and the impinger liquid. On this slide, you can see impingers with the standard nozzle and the arrow points to the so-called FRITTED nozzle. Fritted nozzles have thousands of small holes to disperse the air as it is drawn in with the pump. The creation of many bubbles allows for better contact between the air sample and the impinger collection liquid. Technically, impingers with fritted nozzles are called BUBBLERs and you may see this terminology in published methods.

SAMPLE COLLECTION WITH IMPINGERS
A sample pump is used to bubble air through the impinger which contains a liquid reagent that has been specified in the method. The liquid will physically dissolve or chemically react with the chemical of interest. With impinger sampling, the sample pump is used to bubble air through the impinger which contains a liquid reagent that has been specified in the method and supplied by the lab. The liquid will physically dissolve or chemically react with the chemical of interest. Impingers are not very convenient for personal sampling, but can be useful for area sampling. Always be sure and use a trap of some kind to protect the pump from any spillage of the collection liquid. Trap

CHEMICALLY TREATED FILTERS INTRODUCTION
Alternative to wet chemistry methods Filters are used as a substrate for liquid media that can trap contaminants. Liquid media will chemically derivatize the contaminant of interest. Result is a more stable compound for storage and analysis. In recent years, chemically treated filters are being used as an alternative to wet chemistry methods using impingers. In this case, the filters are not being used for their sieving action, but simply as substrates for liquid reagents that can trap designated contaminants. The liquid media on the filter will derivative the contaminant of interest producing a stable compounds for storage and analysis.

SAMPLE COLLECTION WITH COATED FILTERS
SKC supplies chemically coated filters preloaded into cassettes for designated agency methods.

TREATED FILTERS COMMONLY USED TYPES
Chemical Treatment of Glass Fiber Filters 2,4 DNPH 1-(2-pyridyl) piperazine Sulfuric Acid Mercuric Acetate Applications Glutaraldehyde Diisocyanates (HDI,MDI,TDI) Aromatic Amines Mercaptans Some of the most commonly used treated filters are shown in this slide. For example: Glass fiber filters are treated with 2,4 DNPH for glutaraldehyde. Glass fiber filters are treated with 1-2 pyridyl piperazine for diisocyantes including HDI, MDI, and TDI.

TREATED FILTERS ADVANTAGES
Sample is integrated over the entire period of exposure. Published methods exist with extensive testing and documentation. Workplace compliance officers use these methods for some compounds. Air flow is calibrated and measured. Front and back filter can be used in one cassette to determine breakthrough. Like with sorbent tubes, chemically treated filters offer users a number of advantages: Read slide

SAMPLE BAGS INTRODUCTION
Used since the 1950’s to collect a fixed volume of an air-contaminant mixture into a flexible container for subsequent analysis Called “grab” samples in industrial hygiene and “whole air” samples in environmental field. Sample bags are useful collection devices for an air-contaminant mixture. The term “grab sample” is frequently used by industrial hygienists to describe bag samples while environmental professionals tend to use the term “whole air” sample.

SAMPLE COLLECTION WITH SAMPLE BAGS
Bag samples can be collected using positive or negative pressure techniques. With the positive pressure technique, the air sample is drawn through the pump and then PUSHED into the sample bag through a pressure port on the pump. With the negative pressure technique, the bag is placed inside of a rigid container like the SKC Vac-u-chamber. When the lid is closed, the chamber is essentially airtight. A pump is used to pull all the air from the chamber. This causes air to be drawn from the sample site into the bag. The advantage of this method is that the air contaminants never contact the pump to cause contamination concerns. Positive Pressure Negative Pressure

SAMPLE BAGS SPECIFIED IN SAMPLING METHODS
Nitrous Oxide by NIOSH 6000 Sulfur hexafluoride in NIOSH 6602 Trichloroethylene in NIOSH 3701 Various hydrocarbons in EPA 0040 and EPA SOPs Benzene in NIOSH 3700 Carbon Dioxide in OSHA ID 172 Carbon Monoxide in OSHA ID 210 Ethylene Oxide in NIOSH 3702 Sample bags are specified in the following methods for the collection of designated target compounds. The SKC website has extensive storage stability data for various compounds in a number of SKC sample bags. See this data on our homepage at skcinc.com. Also see for SKC studies on bags.

SAMPLE BAGS BAG MATERIAL OPTIONS
Tedlar®-Classic bag for 1-2 day storage of organic vapors. SamplePro FlexFilm-Tedlar alternative; Useful for storage times ≥3 days for many organic vapors. FlexFoil -Useful for gases such as CO, CO2, H2,methane, and hydrogen sulfide FlexFoil Plus-Suitable for all the same gases as FlexFoil (above) PLUS organic vapors Sample bags are available in a variety of materials depending upon the target compounds. Tedlar bags have been the classic bag for storage of organic vapors for many years. This material was unavailable for a short time but has been reintroduced into the market. SKC now offers Tedlar bags in a choice of fittings. Bags made of Tedlar alternatives are also available from SKC. SKC FlexFILM bags are a cost-effective option with very low background levels of VOCs. SKC FlexFOIL Plus bags provide a versatile option for users who want to collect both gases such as methane and hydrogen sulfide as well as organic vapors in a rugged multi-layer foil bag.

SAMPLE BAGS APPLICATIONS
Leaks, spills, emergency situations requiring rapid collection and analysis Peak concentrations from specific plant processes or worker tasks Field applications using on site portable, direct-reading instruments like PIDs Gases or highly volatile compounds for which sorbent tubes are not suitable Sample bags find application in many health and safety investigations including: Read slide.

STAINLESS STEEL CANISTERS: SPECIFIED IN EPA VOC METHODS
Canisters have been used as an air collection vessel for measurement of low level VOCs. The interior of the canister is treated in some way so that it does not react with collected compounds. Another whole air sampling method involves the use of stainless steel canisters for sample collection. Canisters are widely used by environmental professionals as collection vessels for low level VOCs. Various brands of canisters use proprietary electro polishing procedures like the SUMMA process to make the interior of the device inert. This ensures that the canister does not react with the collected compounds.

STAINLESS STEEL CANISTERS: SPECIFIED IN EPA VOC METHODS
The canister sampling train includes: Stainless steel sampling inlet Particle filter Critical orifice Flow controller A vacuum gauge is used to visually monitor canister status during sampling. Here you can see the critical components for canister sampling: The Sampling Inlet- is cleaned stainless steel tubing that faces downward in this case to prevent rain from being drawn in. The Particle filter-prevents airborne particles from entering that could obstruct the flow path and alter flow rate. A Critical orifice restricts the flow rate to a specified range A Flow controller maintains a constant flow rate over the desired time period. Finally , a vacuum gauge is used to visually monitor changes in canister vacuum levels during sampling. Source:

CANISTER SAMPLING: THE BASICS
Most canister sampling is done “passively” using a canister that has been evacuated to a specified vacuum level. Prior to sample collection, a qualified laboratory should clean and certify the canister, evacuate the canister to the appropriate level, and provide sample identification. At the sampling site, the valve is opened and air flows from the environment into the canister without the need for a pump. Most canister sampling is done “passively” using a canister that has been evacuated to a specified level prior to use. Once the valve is opened, the air flows from the test environment into the canister without the need for a pump. Before you begin a canister sampling program, you will need to have a laboratory partner who has the equipment and expertise to set up and analyze these devices. The laboratory will have the equipment to: -Clean the canister -Certify it is clean -Evacuate the canister to the specified vacuum level prior to sampling

SAMPLING MEDIA: ACTIVE SAMPLING FOR PARTICULATES
Next, we’ll review sampling media for active sampling of particulate matter found in the workplace.

DEFINING PARTICULATES
Solid and liquid matter such as: Dusts-particles rendered airborne during crushing or grinding of rock-like material Fumes-airborne solid particles formed above molten metal Mists-droplets rendered airborne by bubbling, boiling, spraying or splashing Smokes-particles resulting from incomplete combustion of organic matter Particulates in the workplace can be found as dusts, fumes, mists, or smokes and each of these has a scientific definition. Read slide.

THE HAZARD POTENTIAL OF AIRBORNE PARTICULATES
Determined by: Chemical composition Mass concentration Size characteristics The hazard potential of particulates is determined by: Chemical composition-What is it? Mass Concentration-How much is in the air? Size characteristics-How big are the particles?

SIZE CHARACTERISTICS OF AIRBORNE PARTICULATES
Determine the deposition site in the respiratory tract. Smaller particles will tend to deposit deep into the gas exchange region of the lung. Particle size is important because this will determine the deposition site in the respiratory system. Smaller particles will tend to deposit deep into the gas exchange region of the lung.

SIZE-SELECTIVE EXPOSURE GUIDELINES
To more appropriately assess the possible health effects of airborne particulate matter, exposure guidelines have been issued for different sizes of particles. Since particle size will influence the ultimate health effects, exposure guidelines have been issued for different sizes of particles.

TRADITIONAL PARTICULATE SIZE-SELECTIVE CRITERIA
Total Dust Respirable Dust Traditionally, particulates have been described as either TOTAL DUST or RESPIRABLE DUST. Note that in this case, the use of the word dust is just a general descriptor for all particulates.

TOTAL DUST DEFINED Dust that is captured onto a 37-mm filter loaded into a cassette and connected to a sampling pump calibrated to a flow of at least 1 L/min. The filter should be of a type and pore size appropriate to the particulate being sampled. Samples are collected in an area or in the breathing zone of workers. Read slide.

TOTAL DUST SAMPLING IN THE BREATHING ZONE
Here you can side an exploded view of the filter cassette in place. Note that the inlet of the filter cassette should be pointing down during sampling. This ensures that the contaminant mass collected on the filter is what the pump actually pulls in and not what lands onto the filter via impaction from splashing, blasting, or other activities. INLET

TYPES OF FILTER MEDIA MIXED CELLULOSE ESTER
APPLICATION Asbestos, Fibers 25-mm with Conductive Cassette Metals 37-mm with SAN Cassette Oil Mist (Mineral) ANALYSIS Cleared, Microscopic Analysis Digested, Atomic Absorption or ICP Infrared Spectrophotometry The type of filter will depend on the contaminant of interest and it will be specified in the sampling and analytical method. Mixed cellulose ester filters are widely used in industrial hygiene sampling. Applications include asbestos, metals such as lead, and oil mist.

TYPES OF FILTER MEDIA POLYVINYL CHLORIDE
APPLICATION Particulates, Not Otherwise Classified Silica Chromic Acid and Hexavalent Chromium ANALYSIS 2-hour + equilibration, weighing X-Ray Diffraction or Spectrophotomery Visible Absorption Spectrophotometry or Ion Chromatography PVC filters are also widely used for gravimetric analysis of particulates not otherwise classified. They are also the filter of choice for silica, chromic acid, and hexavalent chromium sampling.

TYPES OF FILTER MEDIA GLASS FIBER/QUARTZ
APPLICATION Pesticides Coal Tar Pitch Volatiles, Selected PAHs PCB’s Mercaptans, Isocyanates and more when coated ANALYSIS Gas Chromatography High-Performance Liquid Chromatography (HPLC) Glass fiber or quartz filters are used for specialty applications in industrial hygiene. These filters are specified in sampling methods for pesticides, PAHs, and PCBs. Some IH methods specify CHEMICALLY COATED glass fiber filters for the collection of target compounds including mercaptans and isocyanates.

TYPES OF FILTER MEDIA PTFE
APPLICATION Select PAHs Ambient particulates ANALYSIS HPLC Gravimetric PTFE filters are used for some applications including: -PAHs and -Particulate matter in ambient air

CLOSED-FACE VS OPEN-FACE SAMPLING WITH CASSETTES
Closed-face sampling refers to sample collection with the inlet piece of the filter cassette in place. Open-face sampling refers to sample collection with the inlet removed. This approach is used for asbestos using 25-mm conductive cassettes. Sampling with filter cassettes can be done either closed-face or open-face. For most applications, closed faced sampling is done. In this case, the inlet piece of the filter cassette remains in place during sample collection. Open-face sampling is typically done when sampling asbestos or other fibers. In this case, the inlet piece is removed during sample collection to ensure even distribution of the particles on the filter. Note also that open-face sampling is done when using SKC cyclones. In this application, the inlet piece of the cassette is removed and the cyclone is inserted into the middle ring of the cassette during sampling. After sampling the inlet piece is put back onto the filter cassette for shipment to the lab.

RESPIRABLE DUST DEFINED
Also collected onto a filter of a type and pore size that is appropriate for the particulate being sampled (typically PVC filters). Preceding the filter, however, is a particle size-selective device, typically a cyclone, that will separate the respirable fraction from the non-respirable fraction when connected to a pump sampling at the designated flow rate. Now let’s discuss respirable dust. Respirable dust particles are those small enough to penetrate down to the lower region of the lung. To sample respirable dust, the same PVC filter used for toal dust sampling is used. Preceding the filter, however, is a size-selective device, typically a cyclone. The cyclone will separate the respirable fraction from the non-respirable fraction.

CYCLONES Named for the rotation of air within a chamber
Function on the same principle as a centrifuge Use rapid circulation of air to separate particles according to their aerodynamic diameter Cyclones function on the same principle as a centrifuge. They use rapid circulation of air to separate particles according to their aerodynamic diameter.

WHY USE A CYCLONE? Some chemicals are regulated as respirable dust and cyclones enable collection of the respirable fraction. Collecting larger, non-respirable particulates would inflate results of sample, overestimating exposure. If you are wondering when or why to use a cyclone, the answer is simple. Cyclones are used to sample contaminants like silica that are regulated as respirable dust. Collecting larger, non-respirable particulates with a total dust sampler would inflate results, over estimating exposures.

CYCLONE OPERATION Air enters through a slit on the side of the cyclone which creates cyclonic action. Large particles fall into red “grit pot” and are discarded. Small particles are thrown onto the filter for analysis. Here’s how they work: The sampling pump is attached to the cyclone and it draws air through a slit on the side of the sampler. This creates cyclonic action within the device. Through centrifugal force, larger non-respirable particles fall into the red so-called grit pot and are discarded. Smaller, respirable particles are thrown onto the filter and are sent to the lab for analysis. Red cap must be in place.

50% CUT-POINT: A PERFORMANCE SPECIFICATION
The 50% cut-point is often used to describe the performance of size selective samplers. It is the particle size that the device can collect with 50% efficiency. Particles smaller than the 50% cut-point of the cyclone are collected with an efficiency greater than 50%. Larger particles are collected with an efficiency less than 50%. You will often hear the term 50% cut-point to describe the performance of size-selective samplers like cyclones. The 50% cut-point is the particle size that the device collects with 50% efficiency. Read right side of slide.

DIFFERENT CYCLONE OPTIONS
All cyclones are not created equal! Each cyclone has different operating specifications and performance criteria. Be sure you know the flow rate specified to achieve the desired cut-point before using a cyclone. Keep in mind that there are several types/brands of cyclones on the market. Read slide.

CYCLONES AND AGENCY METHODS
Currently, the only cyclone that OSHA inspectors can use is the nylon Dorr-Oliver at 1.7 L/min. The NIOSH method for respirable dust specifies the use of three cyclone options including the SKC aluminum cyclone at 2.5 L/min. At this time, the only cyclone that U.S. federal OSHA field inspectors can use is the nylon Dorr-Oliver cyclone that was written into the Code of Federal Regulations many years ago. The NIOSH method, however, specifies three cyclone options including the SKC aluminum cyclone at 2.5 L/min. Users should exercise their own professional judgment in choosing a cyclone to meet current definitions of respirable dust. SKC can provide technical assistance as needed.

NEW PARTICULATE SIZE-SELECTIVE CRITERIA
Adopted by many Global Occ Hygiene Agencies including ACGIH: Inhalable Particulate Mass Thoracic Particulate Mass Respirable Particulate Mass Around the world, many occupational hygiene agencies have abandoned the size-selective sampling criteria of total dust and respirable dust. Instead, new particulate size-selective criteria has been adopted defining particulate matter as either: Inhalable, Thoracic, or Respirable Particulate Mass.

Here you can see a diagram of these 3 particulate fractions.

INHALABLE PARTICULATE INTRODUCTION
The “new total”. Term used to describe particulate matter that is hazardous when deposited anywhere in the respiratory system. This includes particulate matter that enters the head airways region including the nose and mouth. Also includes materials that can produce systemic toxicity from deposition anywhere in the respiratory system. Let’s now take a closer look at these particulate sizes. Inhalable is essentially the “new total” dust. Inhalable particulate mass is defined as particulate matter that is hazardous when deposited anywhere in the respiratory system. This includes the larger particles that may get stuck in the nose and mouth as well as small particles that can get down deep into the lung producing systemic toxicity.

INHALABLE SAMPLERS Defined as having a 50% cut-point of 100 microns.
Traditional filter cassettes do not effectively capture inhalable particulate matter. The efficiency of filter cassettes falls to zero with particle sizes of 30 um and larger. Of additional concern are sample losses that occur from particles that adhere to the interior cassette walls. By definition, inhalable samplers have a 50% cut-point of 100 microns. Note that traditional filter cassettes do NOT effectively capture inhalable particulate matter as they tend to UNDERSAMPLE larger particles. The sampling efficiency of filter cassettes falls to zero with particle sizes of 30 um and larger. In addition, sample losses can occur from particles that adhere to the interior cassette walls.

INHALABLE SAMPLERS: DESIGNED FOR THE NEW CRITERIA
The first personal sampler specifically designed for inhalable particulate mass was developed by Mark and Vincent in 1986 at the Institute of Occupational Medicine in Scotland. The sampler was named the IOM sampler and SKC Ltd. in the UK was the sole licensee and exclusive manufacturer of this sampler for more than 20 years. The patent has now expired, but SKC is still the only company that can call this device the IOM Sampler. Read first 2 bullets.

IOM SAMPLER A GOLD STANDARD
The IOM Sampler was the first inhalable sampler and it remains the gold standard. Here you can see the sampling head along with an exploded view of the cassette. Exploded View SKC A

USING THE IOM SAMPLER GRAVIMETRIC ANALYSIS
Load a 25-mm filter into the cassette using forceps and wearing gloves. Do not desiccate the filter/cassette. Equilibrate the filter/cassette assembly overnight under controlled humidity conditions then weigh them as a unit. Allow the assembly to stabilize a few minutes before taking a reading. For gravimetric sampling with the IOM, load a 25-mm filter into the cassette using forceps and wearing gloves. Do not dessicate the filter and cassette. Simply equilibrate the filter/cassette assembly overnight in your weighing room under controlled conditions. Then weigh the filter cassette and filter together as a unit.

USING THE IOM SAMPLER GRAVIMETRIC ANALYSIS
Place the IOM cassette/filter assembly into the sampler body, screw on the cover cap, and connect to the pump. Calibrate the flowrate to 2 L/min using the IOM calibration adapter or by placing in a calibration jar. Following sample collection, weigh the cassette/filter assembly again. Then place the cassette filter assembly into the sampler body, screw on the cap, and connect to the pump. Calibrate the flow rate to 2 L/min for sample collection. Like with all size-selective samplers, the flow rate is critical. Any deviations from this recommended flow rate will alter the collection characteristics of the sampler. Following sample collection, weigh the cassette filter assembly again as described previously.

INHALABLE SAMPLERS BUTTON SAMPLER
Alternative to the IOM sampler for inhalable particulates Inlet has a screen to keep large particles from landing onto the filter by blasting, splashing, or other inadvertent actions. Since the IOM was first developed in 1986, alternative inhalable samplers have also been developed. Here you can see another inhalable sampler from SKC called the Button Sampler. The SKC Button Sampler offers the advantage of a screen over the inlet to keep large particles from landing onto the filter by blasting, splashing, or other inadvertent actions. SKC

SAMPLE COLLECTION WITH BUTTON SAMPLER
A 25-mm filter is pre-weighed and loaded onto the stainless steel screen. The sample is collected at 4 L/min. The sample is weighed again after sample collection to determine exposure levels. With the Button Sampler, a 25-mm filter is loaded directly onto a stainless screen. There is no actual cassette. Then the sample is collected at 4 L/min and weighed again for analysis.

THORACIC PARTICULATE INTRODUCTION
Materials that are hazardous when deposited anywhere within the lung airways and the gas-exchange region. Thoracic samplers have a 50% cut-point of 10 um. Now let’s discuss thoracic particulate matter. Thoracic particulates are defined as materials that are hazardous when deposited anywhere within the lung airways and the gas-exchange region. Thoracic samplers have a 50% cut-point of 10 um.

THORACIC SAMPLERS OPTIONS
SKC offers an impaction based sampler for thoracic particulate called the Parallel Particle Impactor or PPI. The thoracic PPI is used with a suitable 37-mm filter at a flowrate of 2.0 L/min. SKC offers an impaction based sampler for thoracic particulate called the Paralled Particle Impactor or PPI. The PPI is a size-selective device that can be used with any 37-mm filter suitable for collecting the target compound. This slide shows the REUSABLE PPI made from anodized aluminum. Beginning in 2013, SKC will also offer a DISPOSABLE plastic version of the PPI pre-assembled with sampling media. Contact SKC for complete ordering information. SKC U.S. Patent No. 7,073,402

PARALLEL PARTICLE IMPACTOR: HAS 4 INLETS OF DIFFERENT SIZES
Each impactor consists of an inlet nozzle and exit orifice that are appropriately sized to achieve a designated cut-point. The performance of each impactor matches part of the collection efficiency curve so that the overall performance closely matches the entire curve. Inlet Impaction Plate Clarify: The overall performance means: The PM collected on the final filter Exhaust with Final Filter

THORACIC SAMPLERS APPLICATIONS
Thoracic TLVs Sulfuric Acid Cotton Dust NIOSH Methods NIOSH Method 5524, for metalworking fluids specifies a 2-um PTFE filter in a 37-mm filter cassette with an optional thoracic particulate cyclone. Here you can see applications for thoracic samplers: As of 2012, there are two thoracic TLVs for sulfuric acid and cotton dust. AND one NIOSH method using an optional thoracic sampler for metalworking fluids.

DEFINING RESPIRABLE Throughout the history of occupational air sampling, several definitions of “respirable” particulate matter have been proposed by different organizations in various countries. The main difference in the definitions is the 50% cut-point i.e. what size of dust is considered “respirable”. Finally, let’s discuss the last particulate size fraction---Respirable particulate mass. Read slide.

SPECIFICATIONS FOR RESPIRABLE DUST SAMPLERS
The British Medical Research Council (BMRC) originally specified samplers with a 50% cut-point of 5 microns. In the US, government agencies including OSHA/MSHA specify samplers with a 50% cut-point of 3.5 microns. For example: Read slide.

SPECIFICATIONS FOR RESPIRABLE DUST SAMPLERS
To reach world-wide consensus on the use of respirable dust samplers, a compromise spec was developed with a 50% cut-point of 4 microns. ACGIH and NIOSH have adopted this compromise spec. OSHA and MSHA require a change to the federal regulation to make this change from 3.5 to 4.0 um cut-point. Read slide.

RESPIRABLE DUST Conflict and confusion in the USA NIOSH ≠ OSHA
50% cut-point of respirable samplers It is particularly confusing in the USA right now because OSHA and NIOSH do not agree on the 50% cut-point for respirable dust samplers. OSHA is still using the older specification of a 3.5 um cut-point. NIOSH methods specify cyclones with the newer, more conservative 4 um cut-point.

CYCLONES LISTED IN CURRENT NIOSH METHODS
Nylon at 1.7 L/min Higgins-Dewell at 2.2 L/min At the current time, all NIOSH respirable dust methods list 3 cyclone options: Nylon Dorr-Oliver at 1.7 L/min Higgins-Dewell at 2.2 L/min

CYCLONES LISTED IN CURRENT NIOSH METHODS
Aluminum at 2.5 L/min Each cyclone has different operating specifications and performance criteria. Be sure you know the flow rate specified to achieve the desired cut-point before using a cyclone. OR The SKC aluminum cyclone at 2.5 L/min. Read right side of slide. SKC

TIPS FOR SAMPLING: WITH SKC Al OR GS CYCLONES
Prepare 3-piece filter cassette. Place cyclone into middle ring. Calibrate the pump with sampler in line. Take sample at specified flow rate. Remove filter & cyclone from sample train. Replace inlet piece and send filter cassette to the laboratory for analysis. When using SKC cyclones, please keep in mind the following technical tips.

TIPS FOR CALIBRATION Calibration adapter
The Aluminum cyclone has a calibration chamber that fits over the stem of the cyclone which allows standard tubing to be attached for connection to the pump calibrator. As we discussed previously, the SKC aluminum cyclone has a calibration adapter that fits over the stem of the cyclone. This allows for easy connection to the pump calibrator. SKC

TIPS FOR CALIBRATION Calibration Jar
Calibration jars can also be used. But do not use an extremely large jar with the piston style calibrators. The dead volume in the jar can affect the rise/fall of the piston causing the readings to be erroneously low! Calibration jars can also be used to calibrate the flowrate with any cyclone, but do not use an extremely large jar. The standard size calibration jar from SKC is sufficient for the SKC GS cyclone and most others. If you use an extremely large calibration jar, the so-called dead volume in the jar can affect the rise/fall of the piston on dry calibrators causing the readings to be erroneously low. SKC

TIPS FOR CALIBRATION Consider the “jarless” calibration method when using piston-style primary calibrators. Attach cyclone to calibrator pressure port and pump to suction port. A simple alternative is to do the jarless calibration method when using piston-style primary calibrators. Attach the pump only to the normal suction port and attach the cyclone/filter assembly only to the other port, then take the flow measurement.

POST-SAMPLE CLEANING After sampling, clean all parts of the cyclone, with mild soapy water Don’t forget to clean the grit pot. Dry the cyclone. (Air-dry or blow-dry) Wipe with a dust-free tissue or wipe with an isopropyl alcohol moistened pad. Caution: Do not use strong solvents to clean plastic cyclones After sampling, clean all parts of the cyclone with mild soapy water. A build-up of dust inside can alter the cut-points and adversely affect the results.

THANK YOU FOR YOUR ATTENTION!
with any technical questions. Thank you very much for your attention. We hope that you have learned a lot about active sampling. CONTACT SKC WITH ANY QUESTIONS about sampling equipment or methodology.

ACTIVE AIR SAMPLING FOR CONTAMINANTS IN THE WORKPLACE

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