Indoor air quality (IAQ) in the workplace is the subject of much attention these days, and for good reason. The air quality of the indoor environment can profoundly affect the health, comfort, and productivity of building occupants. Although serious health problems related to IAQ are rare, the perception of endangered health is increasingly common among building occupants.
The causes and consequences of poor IAQ are complex and not completely understood, but there are some basic factors that building owners, managers, employers, and occupants should know in order to address IAQ concerns.
What do we mean by “good” IAQ?
Most occupants barely notice when indoor air quality is “good,” but most people will often recognize when the air is not good. IAQ is a problem when the air contains dust and objectionable odors, chemical contaminants, dampness or mold. Related to this are the physical characteristics of the air: the amount of air movement, its temperature and its humidity. General guidelines for achieving good IAQ include:
Ventilation is in accordance with the current guidelines established in the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 62.1, Ventilation for Acceptable Indoor Air Quality.
Comfort factors (i.e., temperature, humidity, air movement) in a range that is acceptable to most occupants, such as published in ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy.
Mechanical equipment and building surfaces are maintained in sanitary condition.
Significant emission sources, such as large copy machines, are separated from occupied spaces and air intakes.
Major sources of chemical or biological contamination are promptly identified and controlled.
Occupied areas are regularly cleaned and good housekeeping practices are in place.
Operations, maintenance, and construction activities are performed in a manner that minimizes occupant exposure to airborne contaminants.
Common Complaints about IAQ
The most common complaint is related to temperature: the air is either too hot or too cold. The second most common complaint is about air movement: the air is either too drafty or too still. Other common comfort-related complaints involve humidity: the air is too dry or too muggy.
Some health-related complaints associated with poor air quality mimic those of the flu or a cold: headaches, sinus problems, congestion, dizziness, nausea, fatigue and irritation of the eyes, nose or throat. Such symptoms are often difficult to associate with the workplace. The indoor environment is usually not the suspected cause of occupant symptoms unless the symptoms are shared by a number of occupants, found to be unreasonably persistent or there is a distinct and suspect odor or other unusual quality to the air.
Some health-related complaints may be due to allergic reactions. Typical indoor allergens include dust mites, cat dander, and mold spores. When exposed to such allergens, 10 percent or more of the population may exhibit symptoms including sneezing, swollen airways or asthma-like attacks. Individuals with a building-related allergy will experience similar symptoms in other environments if the particular allergen is present in both places.
When are IAQ complaints most likely?
Factors associated with an increased likelihood of complaints include the installation of new furnishings, uncontrolled renovation activities, poor air circulation, and persistent moisture. Complaints may also increase when there is a stressful work environment, such as impending layoffs, a great deal of overtime, or an ongoing employee/employer conflict.
Common sources of IAQ problems
Contaminants may originate from a variety of sources both inside and outside of a building, and may include airborne chemicals, bacteria, fungi, pollen and dust. Although they are not indoor pollutants, factors such as temperature, humidity, lighting, noise and personal and work-related stress can affect occupants’ perceptions of indoor air quality.
Potential sources of contaminants in office buildings include dust; inadequate design or maintenance of heating, ventilation and air-conditioning (HVAC) systems; cleaning chemicals, which may contain irritant vapor and/or volatile organic compounds, or VOCs; pesticides; building materials; office equipment such as copy machines and printers; furnishings; occupant metabolic wastes (respiration and perspiration); fragrances/cosmetics; and tobacco smoke. Of course, virtually all of these are present to some degree in every building. They cause IAQ problems only when concentrations become excessive, usually as a result of being generated at a greater rate than they can be removed by the building’s ventilation system.
Occupants may also unknowingly bring potential contaminant sources into the building on their clothing and their bodies, including dust, consumer products (cleaners, air fresheners, personal hygiene products, etc.) and allergenic particles from their homes, such as cat or dog dander. What occupants do may also affect IAQ, such as blocking air ventilation grills, overusing office chemical products and improperly storing food, which may lead to odors and vermin infestation.
Dusty surfaces, stagnant water, and damp materials provide a favorable environment for microbial growth. When odorous compounds resulting from microbial growth and other microbial particles become airborne, some building occupants may experience foul odors and symptoms including allergic reactions. One potential, but rare infection is caused by Legionella bacteria. Exposure to the Legionella bacteria can cause building-related illnesses (Legionnaire’s disease and Pontiac fever) that can be diagnosed through medical tests.
Cigarette smoke contains fine particulate matter, carbon monoxide, formaldehyde, and thousands of other chemicals. Studies have shown that exposure to secondhand tobacco smoke may result in inner ear infections, asthma and lung cancer in nonsmokers. The U.S. EPA has listed tobacco smoke as a confirmed cancer-causing agent. With more restricted smoking regulations in public areas and workplaces, this exposure has decreased greatly. However, the increased use of electronic cigarettes indoors may contribute new sources of indoor air contaminants including nicotine, as well as flavor and fragrance additives.
Contaminants may also originate outside the building and enter via the outdoor air intakes or, when more air is removed by the HVAC system from the building than is supplied, creating a negative pressure in the building compared to outdoors. This pressure difference causes unconditioned air to flow into the building through any available gap. Contaminants can also be sent through a building—sometimes with disastrous consequences-- from boilers, water heaters and other combustion sources that are not properly ventilated.
Why is ventilation important?
Poor IAQ may develop when not enough fresh air is introduced to reduce contaminant concentrations. The HVAC system must not only control contaminants, it must also provide a comfortable environment. The perception of still or stale air, odors, draftiness or errant temperature and humidity levels leads to discomfort. Discomfort, however subtle, can be the beginning of IAQ complaints. Many IAQ complaints originate with the HVAC system failing to meet occupants’ comfort needs, either by not adequately controlling temperature and humidity levels or by not delivering outside air evenly to occupants.
Studies have shown that communicable diseases like the common cold, influenza and tuberculosis spread more efficiently in poorly ventilated buildings. Proper air filtration is also important. However, most of these kinds of illness are passed from person to person through the air or from contacting viruses or bacteria on surfaces, and thus are largely beyond the control of the building owners. Nevertheless, steps can be taken to limit the spread of serious communicable diseases, for example, including pandemic influenza (“flu”).
What can be done about IAQ Complaints
Occupant concerns should be taken seriously and responded to quickly. First, the following information should be gathered and verified, preferably through interviews with occupants and a visual inspection:
What are the specific complaints?
Where in the building are similar concerns about IAQ occurring?
When does the problem occur?
When and where did it first occur?
Who is affected? Is it isolated, or over a large area?
What health effects or discomfort are occupants experiencing?
Do the health effects cease soon after leaving the building, or over the weekend?
Have those affected seen a physician and, if so, what were the diagnoses (do not violate patient privacy)?
Is there any environmental condition (e.g., weather) or activity (e.g., remodeling, use of the photocopier, spraying of pesticides) inside or outside the building associated with occurrence of the problem?
Has the building engineer or HVAC contractor evaluated the area(s) and, if so, what were their conclusions?
Second, analyze the information. Determine if there is a time or space pattern to the complaints. Conduct a walk-through of the area to identify potential sources of contamination or unusual conditions. Also, consider whether the problem may be linked with an activity or condition inside or outside the building, or a malfunctioning HVAC system. In many cases, the source of the complaints may be readily apparent upon investigation, such as HVAC system air intakes next to an exhaust source or a loading dock, the recent addition of large photocopiers in a small room without proper ventilation system modification, an incorrectly set or broken thermostat, or recent remodeling issues.
It is important to communicate to occupants in a timely manner about what is being done to resolve the IAQ issue and any findings from the investigation.
When should air testing be done?
Carbon dioxide (CO2) testing is often performed during the early stages of an IAQ investigation because people exhale CO2 and if there is not enough outdoor (“fresh”) air in a space, the indoor levels of CO2 will increase. Elevated CO2 concentrations in a building reflect insufficient exchange of "fresh" outdoor air for "spent" interior air, allowing the accumulation of human-source odors, and possibly other contaminants. ASHRAE recommends that the indoor levels of CO2 should be controlled to reduce occupant complaints of human-source body odors. When sufficient outdoor air is supplied in keeping with the ASHRAE recommended ventilation levels, the ventilation is generally considered to be adequate. If it is not possible to directly measure the rate of outdoor air supply, an industrial hygienist can measure the indoor and outdoor levels of CO2 and estimate the adequacy of the ventilation. Note that the occupancy of an area affects the measured CO2 concentration and it should be taken into consideration when interpreting results.
However, this approach does not work in all cases. If a particularly irritating or toxic contaminant is present, the problem can only be resolved through control of the contaminant at its source.
Testing for other contaminants (e.g., particulates, volatile organic compounds, microbes, formaldehyde, and pesticides) may provide valuable information but is recommended only if there is good reason to believe that a contaminant is present (a source has been identified or medical evaluation of occupants so indicates). Air testing for a broad spectrum of potential contaminants is generally unproductive. Carbon monoxide (CO) testing or continuous monitoring, on the other hand, is relatively inexpensive and is strongly recommended if there is any reason to question the proper venting of indoor combustion sources, such as furnaces or water heaters.
Some contaminants of IAQ concern are regulated and some are not. However, typical concentration levels of contaminants found in office workplaces are far below regulated exposure limits.
Usually the greatest value of air testing is in the comparison of the results from different locations within a building, indoors versus outdoors and at different times throughout the day. The data generated may yield information about the origin of the problem and possible solutions.
How IAQ problems can be prevented
Three fundamental measures will greatly reduce the likelihood of IAQ problems: good building and ventilation design, effective building maintenance (particularly of the HVAC system) and thoughtfully designed and executed renovation projects. Every building manager should develop a performance profile of the building ventilation system, including analyses of comfort, ventilation and sanitation. This is accomplished in two primary ways.
Inspecting accessible areas of the system for obvious malfunction, bad design, or contamination
Determining airflow, temperature, humidity, proper occupancy and air balance (pressure differentials) in representative areas (zones or rooms) of the building
The information developed may reveal problems with the building's HVAC system – that is, areas in which the system is clearly not performing on par with the remainder of the building. Beyond the initial system profile, it is crucial that the HVAC system be routinely inspected and maintained. Maintaining good IAQ in a building also requires careful managing of custodial, pest control, and building engineering or contractor maintenance activities.
Prior to initiating remodeling activities, discuss IAQ concerns with architects and contractors. Require that the materials and procedures used minimize airborne contaminants. Select materials and products that have been tested to ensure that they emit no detectable irritants or VOCs when possible. Where feasible, schedule work to minimize the impact on air quality (e.g., perform painting on weekends) and arrange for the ventilation system serving the area to be isolated from the remainder of the HVAC system. If walls are being added or moved in the project area or the number or distribution of occupants is to be greatly changed, have a mechanical engineer design modifications to the ventilation system to meet the new requirements.
What you can do to Control Indoor Air Contaminants
The best method to control indoor air contaminants depends on the source or sources causing the complaints. Source removal or control is generally the most cost-effective solution to the problem. For example, environmental tobacco smoke-related complaints have been eliminated in many municipalities by prohibiting smoking within buildings, or by isolating designated smoking areas and providing them with independent ventilation.
Modification of the ventilation system may also be an effective method of resolving IAQ complaints. Contaminants can be diluted with outdoor air, or contaminants such as radon can be managed by changing air pressure relationships between adjoining areas. Increasing the outdoor air supply to meet the criteria of ASHRAE 62.1 may require design and installation of additional heating, cooling, or dehumidification to prevent comfort or moisture-related problems. However, a well- designed and maintained HVAC system may be able to improve the work environment enough to pay for itself through improved occupant productivity.
Air cleaning may also be used to control indoor air contaminants, particularly when the contaminant source is outside the building. Typically, air cleaning is accomplished by installing higher efficiency air filters in existing HVAC systems. An upgrade in the efficiency of existing filters, if compatible with the HVAC system, can help improve IAQ.
During renovation activities, avoid running combustion appliances, such as propane heaters or fuel-fired generators indoors. Carbon monoxide exposure can be fatal.
Occupants can help improve IAQ by:
promptly reporting unusual odors or discomfort
being aware of weather conditions or other factors associated with periods when IAQ concerns appear
using chemical formulations sparingly and only where dedicated ventilation is provided
not taping off air supply diffusers (since it disrupts proper mixing and distribution of air)
minimizing use of fragrances, scented cosmetics, and air-fresheners
When to Seek Outside Help
If the problem persists even after you have identified and rectified obvious sources, you may want to seek outside assistance. You may also require outside help if the problem requires immediate attention and your resources are limited, or your preliminary investigation reveals little of significance and you don't know what to do next.
Sources of professional help include searching online (suggested keywords include "industrial hygiene" and "engineers-ventilation") or local, state, or federal agencies, such as local or state health departments. For a list of industrial hygiene consultants published semiannually, see AIHA's Consultants Listing or search for your state or local AIHA chapter. In certain cases, assistance from specialists in medicine, lighting, acoustic design, or psychology may be needed.
When evaluating consultants, pay particular attention to their professional background in terms of education, professional credentials, the reputation of their firm, and, most important, demonstrated success in resolving similar situations. Ask for references. Hiring someone to perform a poorly conceived study is worse than a waste of money and time; it may lead to erroneous conclusions and costly remedial efforts of little or no intrinsic worth. If a consultant proposes elaborate and expensive air monitoring without demonstrating to your satisfaction that the resulting data will be meaningful, look elsewhere for assistance.
Indoor air quality concerns are a fact of life for building owners, business owners, managers, and occupants. It is not possible to satisfy every occupant at all times, particularly in the case of thermal comfort. However, it is possible and necessary to provide a work environment that is healthy and safe. Establish clear lines of communication so that IAQ issues can be detected and resolved as soon as possible. A building managed with an eye for preventing IAQ problems greatly reduces the likelihood of chronic discomfort and will likely increase building occupants’ productivity.