INDOOR AIR QUALITY - AND HOW TO IMPROVE IT
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Modern office building are generally considered safe and healthful working environments. However, energy conservation measures instituted during the early 1970s have minimized the infiltration of outside air and contributed to the buildup of indoor air contaminants.
Investigations of indoor air quality (IAQ) often fail to identify any harmful levels of specific toxic substances. Often employee complaints result from 'comfort' items such as cigarette smoke, odors, low-level contaminants, poor air circulation, thermal gradients, humidity, job pressures, lighting, work station design, or noise.
The range of OSHA investigations of indoor air quality problems encompasses everything from complaints by one or two employees to episodes in which entire facilities are shut down and evacuated until the events are investigated and problems corrected.
Complaints are often of a subjective, non-specific nature and are associated with periods of occupancy. These symptoms often disappear when the employee leaves the workplace. They include headache, dizziness, nausea, tiredness, lack of concentration, and eye, nose, and throat irritation.
In approximately 500 indoor air quality investigations in the last decade, the National Institute for Occupational Safety and Health (NIOSH) found that the primary sources of indoor air quality problems are: inadequate ventilation, 52%; contamination from inside the building, 16%; contamination from outside the building, 10%; microbial contamination, 5%; contamination from building fabric, 4%; and unknown sources, 13%.
TYPES OF BUILDING PROBLEMS
Employee complaints can be caused by two types of building problems: sick or tight building syndrome and building-related illnesses.
Sick Building Syndrome is a condition associated with complaints of discomfort including headache; nausea; dizziness; dermatitis; eye, nose, throat, and respiratory irritation; coughing; difficulty concentrating; sensitivity to odors; muscle pain; and fatigue. The specific causes of the symptoms are often not known but sometimes are attributed to the effects of a combination of substances or individual susceptibility to low concentrations of contaminants.
The symptoms are associated with periods of occupancy and often disappear after the worker leaves the worksite.
Building-Related Illnesses are those for which there is a clinically defined illness of known etiology. They include infections such as legionellosis and allergic reactions such as hypersensitivity diseases and are often documented by physical signs and laboratory findings.
TOBACCO SMOKE
Tobacco smoke can irritate the respiratory system. In allergic or asthmatic persons, it often results in eye and nasal irritation, coughing, wheezing, sneezing, headache, and related sinus problems. People who wear contact lenses often complain of burning, itching, and tearing eyes when exposed to cigarette smoke.
Tobacco smoke is a major contributor to indoor air-quality problems. Tobacco smoke contains several hundred toxic substances.
MICROORGANISMS
Microorganisms and other biological contaminants (microbials) include viruses, fungi, mold, bacteria, nematodes, amoebae, pollen, dander, and mites.
Sources: water-damaged materials, high-humidity indoor areas, damp organic material and porous wet surfaces, humidifiers, hot-water systems, outdoor excavations, plants, animal excreta, animals, insects, food, and food products.
Acute health effects: Allergic reactions such as hypersensitivity diseases (hypersensitivity pneumonitis, humidifier fever, allergic rhinitis, etc.) and infections such as legionellosis are seen. Symptoms include chills, fever, muscle ache, chest tightness, headache, cough, sore throat, diarrhea, and nausea.
MAJOR INDOOR AIR CONTAMINANTS
Acetic acid
Sources: X-ray development equipment, silicone caulking compounds.
Acute health effects: eye, respiratory and mucous membrane irritation.
Carbon dioxide
Sources: unvented gas and kerosene appliances, improperly vented devices, processes or operations which produce combustion products, human respiration.
Acute health effects: difficulty concentrating, drowsiness, increased respiration rate.
Carbon monoxide
Sources: tobacco smoke, fossil fuel engine exhausts, improperly vented fossil fuel appliances.
Acute health effects: dizziness, headache, nausea, cyanosis, cardiovascular effects, and death.
Formaldehyde
Sources: off-gassing from urea formaldehyde foam insulation, plywood, particle board, and paneling; carpeting and fabric; glues and adhesives; and combustion products including tobacco smoke.
Acute health effects: hypersensitive or allergic reactions; skin rashes; eye, respiratory and mucous membrane irritation; odor annoyance.
Man-made fibers
Sources: fibrous glass and mineral wool.
Acute health effects: irritation to the eyes, skin and lungs; dermatitis.
Miscellaneous gases
This includes ammonia, hydrogen sulfide, sulfur dioxide, etc.
Sources: microfilm equipment, window cleaners, acid drain cleaners, combustion products, tobacco smoke, blue-print equipment.
Acute health effects: eye, respiratory tract, mucous membrane irritation; aggravation of chronic respiratory diseases.
Nitrogen oxides
Sources: combustion products from gas furnaces and appliances; tobacco smoke, welding, and gas and diesel engine exhausts.
Acute health effects: eye, respiratory and mucous membrane irritation.
Ozone
Sources: copy machines, electrostatic air cleaners, electrical arcing, smog.
Acute health effects: eye, respiratory tract, mucous membrane irritation; aggravation of chronic respiratory diseases.
Volatile organic compounds (VOCs)
VOCs include trichloroethylene, benzene, toluene, methyl ethyl ketone, alcohols, methacrylates, acrolein, polycyclic aromatic hydrocarbons, pesticides.
Sources: paints, cleaning compounds, mothballs, glues, photocopiers, 'spirit' duplicators, signature machines, silicone caulking materials, insecticides, herbicides, combustion products, asphalt, gasoline vapors, tobacco smoke, dried-out floor drains, cosmetics and other personal products.
Acute health effects: nausea; dizziness; eye, respiratory tract, and mucous membrane irritation; headache; fatigue.
IMPROVING INDOOR AIR QUALITY
Indoor air quality can be improved by engineering changes such as source controls, air treatment, and ventilation. A second approach is preventive maintenance. Finally, administrative changes can be made to reduce risk of employee illness or injury due to indoor air quality.
ENGINEERING CONTROLS
Engineering controls include source control, air treatment, and ventilation.
SOURCE CONTROLS
Source control includes substitution, removal, encapsulation, local exhaust ventilation, and use of physical barriers.
Adjust combustion sources such as furnaces or water heaters to ensure proper burning and exhaust to an area where re-entrainment will not occur.
AIR TREATMENT
(the removal of air contaminants and/or the control of room temperature and humidity)
1) the use of filtration, electronic cleaners, chemical treatment with activated charcoal or other sorbents
2) humidity control in range of 20%-60%
3) temperature control in the range of 68-76 degrees F
VENTILATION
Ventilation includes the use of natural, dilution, local exhaust, or increased ventilation efficiency.
The most effective engineering control for prevention of indoor air quality problems is ensuring an adequate supply of fresh outdoor air through natural or mechanical ventilation. Outside air intakes should not be located in close proximity to potential sources of contamination (automobile garages, cooling towers, building exhausts, roadways).
The American Society of Heating Refrigerating and Air-conditioning Engineers (ASHRAE) in its 62-1989 standard recommends 20 cubic feet per minute (CFM) of outdoor air per occupant for offices. For smoking lounges, up to 60 CFM of outdoor air per occupant should be provided.
When possible, use local exhaust ventilation and enclosure to capture and remove contaminants generated by specific processes. Room air in which contaminants are generated should be discharged directly outdoors rather than recirculated.
Ventilation efficiency can be improved by:
a) ensuring that outdoor air supply dampers and room air vents are open.
b) removing or modifying partitions or obstructions which block fresh air flow.
c) rebalancing the system to prevent inflow or outflow of contaminated air due to pressure differentials between rooms.
d) preventing poor distribution of make-up air by proper placement of air inlets and exhausts.
e) using room fans to improve mixing and dilution of pollutants.
PREVENTIVE MAINTENANCE (P.M.)
PM plans for humidifiers, water spray and other HVAC system components should include:
a) checking damper positions and functioning belts, baffles, ductwork, and system balance.
b) measuring airflow and performing necessary adjustment if necessary to meet ASHRAE recommendations.
c) replacing filters on air-handling units at regular intervals.
d) cleaning air-distribution ducts and dampers.
e) replacing damaged insulation.
ELIMINATING MICROBIAL CONTAMINATION
Eliminate or control all known and potential sources of microbial contaminants by prompt cleanup and repair of all areas where water collection and leakage has occurred including floors, roofs, HVAC cooling coils, drain pans, humidifiers containing reservoirs of stagnant water, air washers, fan coil units, and filters.
a) Remove and discard porous organic materials that are contaminated (e.g., damp insulation in ventilation system, moldy ceiling tiles, and mildewed carpets).
b) Clean and disinfect non-porous surfaces where microbial growth has occurred with detergents, chlorine-generating slimicides, or other biocides and ensuring that these cleaners have been removed before air-handling units are turned on.
c) Maintain indoor air relative humidity below 60% (50% where cold surfaces are in contact with room air).
d) Adjust intake of outdoor air to avoid contamination from nearby soil, vegetable debris, cooling towers, or sanitary stacks unless air is adequately conditioned.
ASBESTOS AND RADON
Although acute health effects are not associated with asbestos and radon, we mention them due to recent concerns about their health effects.
Asbestos may be found in: insulation and other building materials such as floor tiles, dry wall compounds, reinforced plaster. During renovation or maintenance operations, asbestos may be dislodged and become airborne. Evaluation of employee exposure to asbestos will normally be covered under the OSHA Asbestos standard.
Radon may occur in the ground beneath buildings, building materials, and groundwater. Chronic exposure may lead to increased risk of lung cancer from alpha radiation.
ADMINISTRATIVE IAQ CONTROLS
Administrative control practices including programs that change the behavioral patterns of occupants.
Minimize Exposure. Exposure should be minimized by limiting occupancy of contaminated airspace, limiting use of offending sources to specific areas or times, or evacuating contaminated areas until they can be ventilated adequately.
1) Isolate, if feasible, areas of renovation, painting, carpet laying, pesticide application, etc., from occupied areas that are not under construction.
2) If possible, perform this work during evenings and weekends. If ventilation is turned off during weekends or other periods, ensure that the system is on so that contaminant concentrations are sufficiently diluted prior to occupancy.
3) Supply adequate ventilation during and after completion of work to assist in diluting the contaminant levels.
4) Personnel affected with hypersensitivity should be thoroughly evaluated and the problem identified and corrected before returning them to the workplace. If, after the remedial action, the illness persists in the workplace, the affected personnel should be considered for permanent reassignment to another area.
Eliminate or reduce contamination of the air supply. This includes contaminants such as cigarette smoke. Ban smoking or restrict it to designated areas that have their air discharged directly to the outdoors rather than recirculated.
Excerpted with permission from SIC Safety Information Currents, Volume III, Number 6, June 1994.