SECTION 6 AIR CONDITIONING (HEATING AND HUMIDIFICATION) UNIT 34 INDOOR AIR QUALITY

UNIT OBJECTIVES After studying this unit, the reader should be able to List sources of indoor air pollution. Explain procedures for eliminating contamination sources. Describe how molds reproduce. Discuss ventilation as it applies to indoor air quality. State two substances needed for mold to grow. Describe air cleaning devices.

UNIT OBJECTIVES After studying this unit, the reader should be able to Discuss reasons for cleaning air ducts. Explain relative humidity. State reasons for providing humidification in winter months. Describe various types of humidifiers. State reasons for installing self-contained humidifiers. List general factors used when sizing humidifiers.

INTRODUCTION Indoor air is often more polluted than outdoor air Many people spend as much as 90% of their time indoors, especially the very young, the very old and the ill ASHRAE Standard determines the acceptable indoor air quality levels

SOURCES OF INDOOR AIR POLLUTION There are many indoor air pollutants Older homes allow pollutants to enter Newer structures are tighter Outside air must be brought into the structure Inadequate ventilation can cause –Window and wall condensation –Formation of mold and smelly, stuffy air

CONTROLLING INDOOR AIR CONTAMINATION Eliminate the source of the contamination Provide adequate ventilation to the structure –Adds and removes air from the structure –Contaminants are removed while fresh air is introduced to the structure –The contamination concentration is reduced Provide a means to clean the air

CONTROLLING INDOOR AIR CONTAMINATION

COMMON POLLUTANTS Radon Tobacco smoke –Second-hand smoke –Contains over 4,000 components Biological contaminants –Dust mites –Mold Lead –Air, water, food, soil Household products –Contain organic chemicals –Paint, varnish, cleaning products Formaldehyde Pesticides Asbestos Pollutants from combustion –Burning fuels –Carbon Monoxide

CONTAMINATION SOURCE DETECTION AND ELIMINATION Various monitoring instruments can detect: Carbon dioxide Carbon monoxide Hydrogen sulfide Sulfur dioxide Chlorine Hydrogen Oxygen Nitric oxide Hydrogen Cyanide Ammonia Ozone Hydrogen chloride

VENTILATION Process of supplying/removing air from an area Proper ventilation improves air quality Outside air must be filtered and heated or cooled Ventilation methods can be natural or mechanical Residences typically have natural ventilation ASHRAE Standard Energy Recovery Ventilators (ERV) Heat Recovery Ventilators (HRV)

HEAT RECOVERY VENTILATOR (HRV) CONFIGURATION Structure wall Exhaust Fresh air intake Intake filter Exhaust blower Air to occupied space Air from occupied space Exhaust filter Intake blower Heat exchanger

AIR CLEANING Mechanical filters –Fiberglass disposable, pleated, cube, pocket, HEPA Electronic air cleaners (Multi-stage) –Pre-filter, ionizing, collection, odor removal Ion generators –Charge particles that then adhere to walls and floors Ultraviolet light (UV-C) –Destroys microbes that create unhealthy air

Fiberglass disposable filter Pleated filter Permanent steel or aluminum filter

TYPICAL ELECTRONIC AIR CLEANER STAGES Prefilter Charging section CollectionCharcoal Large particles captured here Particles are charged here Small particles are collected here Odors are removed here

DUCT CLEANING Ducts should be cleaned if there is visible mold growth, rodent infestation or excessive dust Cleaning includes the ductwork, grilles, diffusers, heat exchangers, coils, condensate pans, fan motors, motor housings and humidifier components Vacuum duct cleaning systems are vented outside Access holes must be resealed upon completion National guidelines should be followed

AIR HUMIDIFICATION Relative humidity is the percentage of moisture in the air compared to the maximum capacity of an air sample to hold moisture Relative humidity falls as temperature increases –Air expands when heated and moisture is spread out –1 ft 3 of air can hold more moisture at higher temps. Recommended humidity for homes is 40 to 60% People can be comfortable at lower temperatures if the humidity is higher

HUMIDIFIERS Evaporative humidifiers – use a wet media –Air is passed over the media and the water evaporates Electrically heated humidifiers –Water evaporated by electric heating elements Infrared humidifiers – –Uses infrared lights reflected onto the water Atomizing humidifiers –Discharges tiny water droplets into the air

SIZING HUMIDIFIERS 1.The number of cubic feet of space to be humidified. 2.The construction of the building. This includes quality 3.The amount of air change per hour and the approximate 4.The level of relative humidity desired.

INSTALLATION Particular attention should be given to clearances within the duct or plenum. If mounting on a supply duct, choose one that serves the largest space in the house. Plan the installation carefully, including locating the humidifier, as already discussed, and providing the wiring and plumbing (with drain). Always check state and local building codes.

UNIT SUMMARY ASHRAE standard determines acceptable indoor air quality levels Air quality can be improved by removing the source of contamination, filtering and ventilating Duct systems should be cleaned if there is excessive dirt, infestation or mold growth Relative humidity is the ratio of moisture in an air sample divided by the capacity of the air to hold moisture Humidifiers add moisture to the air in the structure