Presentation on theme: "Indoor Air Pollution Lecture-1 Mukesh Khare (PhD UK) Department of Civil Engineering Indian Institute of Technology Delhi."— Presentation transcript:
Indoor Air Pollution Lecture-1 Mukesh Khare (PhD UK) Department of Civil Engineering Indian Institute of Technology Delhi
A Common Myth Air pollution occurs only outdoors Or In industrial environment
Truth!!!! What is more agreeable than one ’ s home? Feeling safe ? Away from outside pollution ? Air inside the conditioned space can be substantially more polluted than outdoor air.
Historical Perspective First indication of indoor contamination – Asbestos pollution, a carcinogenic substance, discovered by epidemiologists, used in almost all building materials about 35 years back.Banned due to adverse health effects NOT considering IAQ. Concept of IAQ first introduced among scientific community in 1980 due to some occurrences of ‘episodes indoors’. At central headquarters of EPA building at Washington, D.C.- more than 100 people fell sick within 15 minutes of entering the office. In Los Angeles, CO level in most of the well insulated buildings was three times greater than the outside level.
Outcome Such episodes indoors in developed nations ended up with 1. Extensive monitoring programme development indoors 2. Identification of indoor contaminants 3. Formulation of IAQ models 4. Development of control methodologies 5. Formulation of Indoor Air Contamination Standards. 6. Identification of ‘Sick Buildings’ 7. Investigation of ‘Sick Building Syndrome (SBS)’
What is IAQ?? IAQ stands for “ Indoor Air Quality ”. It refers to the nature of the conditioned (heat/ cool) air that circulates throughout space/area, where we work and live i.e. the air we breathe most of the time (almost 80 % of the time).
What Causes Indoor Air Pollution?? Air tightness of buildings Poorly designed air conditioning and ventilation systems Indoor sources of pollution Outdoor sources of pollution
Air Tightness in Buildings Causes inadequate supply of fresh air, as a result, negative pressure develops, which causes Ground level pollutants, e.g. CO, Radon etc.to be drawn inside the buildings. Release of odor (Bioaerosols) and other pollutants. Pull outside polluted air from vents, cracks and openings and increase dust, pollen etc. Causes “ Sick Building Syndrome ”.
Poorly Designed Air Conditioning Systems Results into the production of fungi, molds and other sickness causing microbes.
Problems of IAQ Enclosed spaces inhabited by humans produce following effects- Reduction in oxygen level of spaces. Increase in CO 2 level. Increase in temperature. Increase in humidity Increase in Bioaerosols and odor
Sources of Indoor Air Pollution in a Typical Office Building
Sources of Indoor Air Pollution in a Typical Household
Hard Facts Fresh air contains 21.0% (v/v) O 2 Exhaled air contains 17.0% (v/v) O 2 and 83.0 % (v/v) CO 2 An adult emits 45 gm sweat / hour containing bioaerosols. An adult produces 300 BTU of heat / hour. Carbon based gaseous pollutants (VOCs) indoors are 2 to 5 times higher than outdoors.
Indoor Air Pollutants and Their Health Effects PollutantEffectsLimits NO 2 Type: Immediate Causes: irritation to the skin, eyes and throat, cough etc. 0.05 ppm (avg. over one year for 8 hours exposure daily)- EPA CO Type: Immediate Causes: headache, shortness of breath, higher conc. May cause sudden deaths. 9.0 ppm (avg. over 8 hours period)- EPA RSPM Type: Cumulative Causes: Lung cancer 150 µ g/ m 3 (24 hr. average) SO 2 Type: Immediate Causes: lung disorders and shortness of breath 0.05 ppm (avg. over one year for 8 hours exposure daily)- EPA Radon Type: Cumulative Causes: Lung cancer >/ 4 pCi/ Litre of indoor air Formaldehyde Type: Immediate Causes: irritation to the eyes, nose and throat, fatigue, headache, skin allergies, vomiting etc. 120 g/ cu.m. (continuous exposure)- ASHRAE Asbestos Type: Cumulative Causes: Lung cancer >/ 2 fibers/ cu.cm. Of the indoor air (8 hrs. exposure period)- OSHA Pesticides Type: Immediate Causes: Skin diseases - VOCs Type: Immediate Causes: Liver, kidney disorders, irritation to the eyes, nose and throat, skin rashes and respiratory problems. Not for all VOCs. For chlordane: 5 g/cu.m.(continuous exposure)) CO 2 Surrogate index of ventilation1000 ppm O3O3 Type: Immediate Causes: eyes itch, burn, respiratory disorders, lowers our resistance to colds and pneumonia. 100 g/cu.m (continuous exposure)- OSHA
PollutantsConcentration reported Concentrations of limited or no concern Concentration of concern Remarks Respirable particulates 0.05 – 0.7<0.1>0.015Japanese standard 0.15 mg/m 3 CO1-1.5<2>5Indicator for eye irritation(only from passive smoking) NO 2 0.05 – 1<0.19>0.32 ---- CO ----2% COHb3%COHb99.9% 1-100<11>30Continuous exposure Formaldehyde0.05 – 2<0.06>0.12Long- and Short- term SO 2 0.02 – 1<0.5>1.35SO 2 alone, short-term CO 2 500 – 5000 ppm<1000 ppm>1000 ppmOccupancy indicator O3O3 600-9000<1800>12000Japanese standard 1800 mg/m 3 Asbestos <10 fibres/m 3 00 10 5 fibre/mFor long Exposure WHO Standards * typical ranges of concentration is given in mg/m 3, unless otherwise indicated
Parameters Affecting IAQ Rate of exchange of air from outdoors (ventilation) Concentration of pollutants in outdoor air Rate of emission from sources indoors Rate of removal of pollutants (Sinks) Indoor temperature Indoor humidity Age of indoor structure Type of foundation soil
Steps for Investigating IAQ Problems Document employee health complaints. Examine floor plans and ventilation system specifications. Analysis of data collected from above steps for SBS score calculations. Study of building layout, position and location of windows, doors, vents, openings etc. Ventilation measurement. Monitoring of indoor pollutants and other environmental parameters and development of IAQ model. Develop a plan for reducing and eliminating the IAQ problem.
What is Ventilation?? A process, whereby air is supplied and removed from an indoor space by natural or mechanical means. Why ventilation is needed indoors? To remove heat or moisture OR to reduce the concentration of one OR more indoor pollutants Types of Ventilation Natural Mechanical
Natural Ventilation Involves Infiltration: random/ intentional flow of outdoor air through windows, cracks and a variety of openings in the buildings. Exfiltration: movement of air from indoor spaces to outdoor. Limitation of Natural Ventilation Fairly inefficient as it is NOT UNIFORMLY distributed. Air doesn’t circulate evenly and stale air gets collected in some dead end spaces. It brings POLLENS & OTHER POLLUTANTS from outside air. Maximum energy loss occurs as NO CONSERVATION of energy can be done.
Mechanical ventilation It involves use of fans and heating / air conditioning equipments. Principle of mechanical ventilation Pulling fresh air from outside to indoor spaces. Exhaust stale air. Control temperature and humidity inside.
Air Flow Inside the Buildings Stagnation zone Air in Air out Air flow, when uniform mixing inside (mechanical ventilation) Air flow pattern, when natural ventilation occurs
Ventilation Measurement A.In naturally ventilated buildings By Infiltration measurement.Infiltration is reported as air change per hour (ACH) – the average rate at which indoor air is replaced by fresh outdoor air.ACH is a rough guideline for different building conditions, given by ASHRAE. For e.g., in “air tight buildings” ACH is 0.1 to 0.2, in “leaky building”, ACH is 2.0 to 3.0. ASHRAE model for measuring infiltration in naturally ventilated buildings is – I = ln (C O / C i ) / t Tracer gas technique is employed to measure infiltration. Non reactive gases, e.g. SF 6 /NO are used as tracer gases with the assumption that the loss of tracer gas is only due to ventilation/ exfiltration. B.In mechanically ventilated buildings ACH is measured by CO 2 concentration. It is a good surrogate index to determine the proper ventilation in HVAC buildings. ASHRAE model for measuring infiltration in HVAC buildings is – Q = G/ C i – Ca Minimum recommended ventilation rate by ASHRAE is 8L/sec. per person to maintain the indoor concentration of CO 2 as 700 ppm.
Parameters for Natural Ventilation Air Flow- occurs mainly due to two driving forces 1. Pressure Gradient – Difference in outdoor and indoor pressure (varies with building shape, size, openings, wind direction, local environmental densities, neighbour building’s configuration, topography etc.) 2. Temperature Gradient (Buoyancy Forces)- when the inside air temperature is higher than outside air, the warm air at floor surface starts rising and the cool air starts entering as a result of vaccum created at floor surface. This effect is called as “Stack Effect”.
Parameters for Mechanical Ventilation Infiltration air Exfiltration air Recirculated air Exhaust air Makeup air
What is sick building syndrome? The feeling of illness among majority of occupants of a conditioned space is called “Sick Building Syndrome”. A variety of illness symptoms reported by occupants in sick buildings are – Headache, fatigue, irritation in eyes, nose and throat, shortness of breathe etc. Causes Inadequate ventilation – insufficient supply of outside air; poor mixing; fluctuations in temperature & humidity; air filtration problem due to lack of maintenance of HVAC systems. The CO 2 level indicates the ventilation efficiency of buildings. Building shows SBS symptoms, if CO 2 concentration > 1000 ppm.