#IAQ Articles

What Affects Indoor Air Quality in Commercial Buildings

When it comes to indoor air quality in schools, hospitals, government offices, private businesses and other commercial buildings, the standards are different from those of residential homes. Commercial buildings are generally much larger and may house a great number of people at one time. This means that the indoor air quality may be affected by many different factors.

It is believed that over the past few decades the number of airborne pollutants inside commercial structures has increased considerably due to a number of factors;

  • HVAC and IAQTightly sealed buildings
  • Reduced ventilation
  • Presence of synthetic building materials
  • More time spent indoors
  • Building deterioration
  • Improper design or maintenance

In essence, with more people staying inside buildings that have reduced ventilation, the chances of being exposed to airborne pollutants has increased significantly over time. However, the basic sources of indoor air pollutants have remained relatively the same.

Sources of Indoor Air Pollution

There are a number of common sources of pollutants that may affect the health of those inside, particularly if they spend several hours per day within the confines of the building. These particles include, but are not limited to the following;

  • Dust
  • Pollen
  • Soot
  • Fibers
  • Mists
  • Aerosols
  • Mold
  • Gases and more

Quite often, the pollutants that affect the indoor air quality come from the HVAC or air conditioning system which is usually the vents. Changes in temperature and humidity may result in the growth of fungus, mold or other substances that find a haven in air vents which are then circulated throughout the building itself. Furthermore, spotting the sources of the pollution can be difficult, especially in vents that do not get regularly inspected or carpets that are not fully cleaned.

This means that the first signs of an indoor air pollution problem will come from the symptoms shown by those who work inside.

The Symptoms of Poor Indoor Air Quality

There are a number of symptoms that business owners and organizational managers will need to keep an eye out for in order to spot potential issues with the air quality.

  • Increase in the number of health issues, particularly those of a respiratory nature
  • Greater absenteeism
  • Loss of productivity
  • Unusual deterioration of equipment and furnishing
  • Increasing behavior issues and more

Generally speaking, increases in the number of health issues that include coughing, sneezing and eye irritations are a sign that something might be negatively affecting the air quality.

How to Address Indoor Air Issues

There are a number of ways that the quality of air indoors can be addressed to reduce the amount of pollutants.

Identifying the source of the pollution and getting rid of it is the most important step. Proper ventilation will help circulate and push out many of the air pollutants and keep them from concentrating in one place. Exhaust systems will force the pollutants out and proper exposure controls will help maintain the overall indoor air quality to acceptable levels.

Taking the proper steps will ensure that the people inside a commercial building will not be exposed to indoor air pollution thanks to regular inspection, maintenance and initiating the proper action.




Share This:

When to Sample VOCs

Sampling for VOCs should only be done after source elimination has been considered as a first step. If this is not possible, or too expensive, sampling could then be considered. The source-pathway-receptor relationship will have characteristics that will influence the sampling method and duration. Table 2-5 shows how VOC sampling can be tailored to suit various complaint patterns.

If the timing of a source is well known it may be used to define the source-pathway-receptor relationship and possibly eliminate or reduce the amount of VOC sampling required. For example, if odour or health complaints can be correlated with building conditions, occupant/neighboring activities, weather, or ventilation system status, then it may be possible to determine the source or pathway, and mitigate the problem without sampling or to adjust the sampling program.

Table 2-5 Complaint patterns and sampling methodology


Sampling / Analysis Considerations


Complaints that occur at specific times should result in sampling that occurs at those times. To allow for pre-concentration prior to analysis short-duration, whole-air sampling followed by VOC characterization may be appropriate.


When complaints are received continuously, short duration sampling followed by VOC characterization (e.g., Austen Method (AM) 1.2) would be appropriate.


Complaints that occur seasonally should be assessed by comparing VOC profiles for both the complaint and non-complaint periods.


Complaints that occur periodically should result in sampling that occurs at those times, sampling duration should be appropriate for event duration.


Erratic complaints are most problematic and may require sampling close to com- plaint areas and providing a means for affected people to quickly advise of reoccur- rences of symptoms.

The duration of sampling should provide data that it is representative and meaningful. How the data will be interpreted should be considered. Timing factors may also be defined by legislation such as determi- ning short-term exposure or time weighted average exposure for workers. Where timing is not defined by legislation, occupants should be interviewed or asked to complete a questionnaire to gain an unders- tanding of when exposure may be occurring. It is important to note that complainants may not always be objective when providing information.

For more information on VOC sampling strategies and methods, go to:  http://iaqforum.ca/wp-content/uploads/2012/11/Mod2_VOC.pdf

Share This:

Commonly Used VOC's and Sources

VOCFor more information on VOC’s, best practices and how to deal with them, go to our Module: http://iaqforum.ca/wp-content/uploads/2012/11/Mod2_VOC.pdf


Share This:

Best Management Practices


Best management practices (BMPs) for indoor air quality are procedures implemented during the planning, construction and operation of buildings to reduce exposure and emission of pollutants. For example, many building operators have established BMPs for maintenance (e.g., air-handling unit filter changes) intended to ensure good IAQ.  BMPs may require VOC sampling in order to determine suitable occupancy or re-occupancy timeframes (e.g., during renovations when VOC levels may be elevated due to the introduction of new materials or prior to occupancy). The appropriate VOC sampling method depends on the source-pathway-receptor scenario for each case. The methods would generally include screening or semi-quantitative methods when quick results and monitoring of control measures are required; and quantitative results when occupancy criteria or certification is required. BMPs have been issued by various authorities, primarily by federal, provincial and municipal agencies. Examples are listed in Table 2-1.

Share This:

Complaint Investigations of IAQ

Air_QualityComplaints by occupants about air quality may require building operators and facility managers to respond with an IAQ assessment that includes VOC sampling. The first step is to use interviews and walk-through inspections to determine symptoms, odours, timing, related activities, as well as building conditions and operation of the heating, ventilation and air-conditioning (HVAC) system.

When assessing complaints it is important to note that feelings of discomfort and illness may be related to health conditions (e.g., the common cold or influenza) or to building issues such as noise levels, ther- mal comfort (temperature, humidity, and air movement), lighting, and ergonomics and many non-buil- ding issues or pre-existing medical conditions.

Poor air quality would be suspected if occupants develop symptoms within a few hours of being in the building and feel better after leaving the building, or after a weekend or vacation. It would also be suspected if several people report similar symptoms, or if all of the people reporting symptoms are in the same area of a building or HVAC zone. VOC exposure symptoms may include:

  • Eye, nose, and throat irritation
  • Headaches
  • Allergic skin reaction like a rash
  • Difficulty breathing
  • Nausea and/or vomiting
  • Nosebleeds
  • Fatigue
  • Dizziness
  • Loss of coordination
  • Confusion

If the initial investigation indicates the possibility that health or odour complaints are related to VOC sources, the sampling method will initially depend on whether the VOC source is known or unknown. Sampling may be needed if further information on the pathway or receptor is required, or if mandated by regulatory concerns or orders. Examples of sources of VOCs are provided in Table 2-3 of Module 2: VOC Sampling Strategies and Methods

Share This:

Volatile Organic Compounds

2005_sources_of_vocsVolatile organic compounds are chemicals that contain carbon, hydrogen and oxygen and are gases at room temperature. The volatility, polarity, water solubility, and reactivity of a VOC affect the choice of sampling methods.

To assess the influence or relevant importance of various factors in determining the indoor VOC concen- trations it is helpful to use a “source-pathway-receptor” conceptual model. The source is the cause of the presence of the VOC. The pathway is the route the VOC takes to a receptor and a receptor is a person, animal, plant, property or eco-system that is exposed to the VOC. Each factor plays a role in determi- ning the final VOC concentration within the indoor air environment.

In general this conceptual model will also help identify any VOC control strategies that may ultimately be required. Indoor VOC concentrations may be controlled by three basic strategies:

• Source control is the avoidance or elimination of materials that emit VOCs;

  • Ventilation is the lowering of VOC concentrations by replacing air in specific spaces with air (fresh air) that has a lower concentration of VOC (for example, dedicated exhausts in garbage rooms or the pressurization of public corridors);
  • Cleaning includes filtration and ultra (UV) radiation. Filtration is the physical capture and dispo- sal of VOCs. Ultraviolet radiation is the chemical alteration of a VOC compound with the inten- tion of creating different and less harmful compounds.

    A sampling program may be required to demonstrate the effectiveness of any control measures that have been implemented.

Share This:

10 Reference Documents for #IAQ

IAQ for buildingsIndoor air quality is a relatively new and an evolving science. Several important reference documents have been created and are available on the Internet. The CCIAQB provides these references as useful sources, but does not endorse the organizations, or the literature and products that are available from them.

1. Building Air Quality: A Guide for Building Owners and Facility Managers:           http://www.epa.gov/iaq/largebldgs/pdf_files/iaq.pdf

2. Pennsylvania Green Building Maintenance Manual: http://www.mass.gov/Eoaf/docs/dcam/mafma/manuals/o_and_m_pa_green_bldg_o&m_manual. pdf

3. Indoor Air Quality: A Guide for Building Owners, Managers, and Occupants, Work Safe BC http://www.worksafebc.com/publications/health_and_safety/by_topic/assets/pdf/indoor_air_ bk89.pdf

4. Environmental Tobacco Smoke (ETS): Workplace Policy, Canadian Centre for Occupational Health and Safety:

5. California Department of Public Health, Indoor Air Quality Program:

6. LEED User:

7. An Office Building Occupant’s Guide to Indoor Air Quality, US EPA:

8. Indoor Air Quality – Action Kit for Canadian Schools, Health Canada:

9. Health Canada (2006). Residential Indoor Air Quality Guideline. Formaldehyde. ISBN: 0-662- 42661-4. Available at:
http://www.hc-sc.gc.ca/ewh-semt/alt_formats/hecs-sesc/pdf/pubs/air/for- maldehyde-eng.pdf

10. IAQ Tools for Schools – Action Kit, US EPA:

For more information on an introduction to IAQ, click here for our downloadable module.

Share This:

Understanding IAQ: Key Factors

This model shows the interrelationship among key factors that are discussed in the series of modules that are part of this guide. A very simple mass balance model based on this figure could be written as:

Understanding IAQ

Consider the following:

Co: introducing contaminated air is a “root cause” of poor air quality. Most filters collect only a fraction of particles present in the air stream and none of the gas contaminants. The quality of the outdoor air and location of the outdoor air intakes relative to potential sources of contamination are critical.

V: ventilation is a basic component of IAQ management and indoor contaminant dilution. During occu- pancy, ventilation should be continuous, reliable and adequate for the types of activities that are being carried out in the building. It is important to maintain good hygienic conditions in the HVAC system to prevent it from becoming a source of contaminants.

K: supply air must be well mixed and distributed in the occupied areas. “Short circuits” not only reduce the efficiency of ventilation, but rob the building of the benefit: money is spent to heat or cool air that did not provide the anticipated level of comfort and air quality for the occupants.

Think about S: reducing or eliminating indoor sources of contamination is an effective and efficient method of maintaining acceptable air quality. It is better, simpler and less expensive to not introduce contaminants than trying to remove the contaminants after they are brought into the building. When selecting any material, furniture or product that will be inside the building, enquire about emissions and custodial requirements (cleaning products, etc.)

Think about R: the removal of indoor sources of contaminants may be active (controlling entry, filtra- tion, custodial practices, etc.) or passive (settling on surfaces, absorption into materials or “sinks”, i.e. places into the space where contaminants are soaked-up). While useful and sometimes necessary, remo- val is not a substitute for inadequate source management.

For more of the basics of Understanding IAQ, download our module by clicking here.

Share This:

Six Basic IAQ Control Strategies

Strategies for controlling the quality of indoor air can be condensed into six basic control methods:

Source Management is the action of identifying, avoiding and isolating or removing a source of air contamination. It is one of the most important strategies because it addresses root causes of IAQ pro- blems.

Local Exhaust involves the removal of point sources of pollutants before they can disperse into the indoor air, by expelling contaminated air directly outside. Sites where local exhaust is used include restrooms and food preparation areas. Other locations where pollutants originate at specific points and can be easily exhausted include storage rooms and photocopying rooms.

IAQ ventilation Ventilation introduces outdoor air into a building to displace or dilute contaminants in the indoor air. Generally, local building codes specify the quantity (and sometimes quality) of outdoor air that must be continuously supplied to an occupied area. For activities such as painting, or in the event of chemical spills, a temporary increase in ventilation can help to dilute the concentration of noxious fumes in the air. In such cases, reducing or eliminating recirculated air is advisable. Ventilation should not be consi- dered as a substitute for proper work practices and other measures that eliminate or control the original source of the pollutants. Ventilation is most efficient and effective when applied to a well-designed and managed facility.

Exposure Control includes adjusting the time and location of building occupancy to minimize expo- sure to intentionally released air contaminants. For example, the best time for stripping and waxing floors may be on weekends. This schedule would allow the floor products to off-gas over the weekend, reducing the level of odours or contaminants in the air when the building is occupied. This strategy may require adjusting ventilation rates which are often reduced during weekends and other unoccupied periods.

Air Cleaning is the capture of particles from the air. Various types and levels of particle filtration are normally included in ventilation systems. Gaseous contaminants can also be removed, but in most cases these types of systems are complex and expensive and should be evaluated on a case-by-case basis.

Education of the building occupants about IAQ is critical. People must be provided with information about the sources and effects of contaminants (including those under their control), and about the proper operation of the ventilation system. With this knowledge, they will better understand their indoor envi- ronment and can take steps to reduce their personal exposure and improve the overall IAQ.

For more of an introduction to indoor air quality (IAQ), visit our introductory module: http://iaqforum.ca/wp-content/uploads/2012/11/Mod1_Intro.pdf 

Share This:

IAQ Definitions and Abbreviations

This post defines common IAQ terms (adapted from the U.S. Environmental Protection Agency (EPA)) and some abbreviations used in many of the modules. Text in square brackets [] has been added by the authors of this document.

Air changes per hour (ACH): the amount of air in a building that leaks out or is removed by a fan and is replaced by outdoor air, usually listed as a fraction of one air change per hour, such as 0.35 ACH. [ACH is sometimes referred to as air exchange rate or AER.]

ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning Engineers.
Building envelope: [the] elements of the building, including all external building materials, windows and walls that enclose the internal space.

EscherichiaColi_NIAIDBiological contaminants: agents derived from, or that are, living organisms (e.g., viruses, bacteria, fungi, and mammal and bird antigens) that can be inhaled and can cause many types of [adverse] health effects including allergic reactions, respiratory disorders, hypersensitivity diseases, and infectious diseases, also referred to as “microbiologicals” or “microbials.”

Carbon dioxide (CO2): a colorless, odorless, and tasteless product of combustion. All combustion processes and human metabolic processes are sources of CO2. Concentrations of CO2 from people are always present in all occupied buildings, and at concentrations normally found in buildings, CO2 is not a health hazard.

Carbon monoxide (CO): a colorless, odorless, and tasteless gas which results from [incomplete] com- bustion of fuels. It is often associated with combustion heating devices (e.g. boilers, furnaces) and auto, truck, or bus exhaust from attached garages, nearby roads, or parking areas. At moderate concentrations, angina, impaired vision, and reduced brain function may result. At higher concentrations, CO exposure can be fatal.

SONY DSCFormaldehyde: Formaldehyde is a colorless water-soluble gas. Due to its wide use, it is frequently considered separately from other VOCs. Materials containing formaldehyde include building materials, furnishings, and some consumer products. [It is also a by-product of combustion.] Formaldehyde has a pungent odor and is detected by many people at levels of about 100 parts per billion (ppb). Besides the annoyance, it also causes acute eye burning and irritates mucous membranes and the respiratory tract. [The risk of cancer associated with formaldehyde levels, sufficiently low to prevent irritation and inflam- matory responses, appears to be negligible (Health Canada, 2006)].

Fungi: any of a group of parasitic lower plants that lack chlorophyll, including molds and mildews.

HEPA: high-efficiency particulate arrestance [air] (filters).

IAQ profile: a base-line description of the features of a building structure, function, and occupancy that impact indoor air quality. A completed IAQ profile provides an understanding of the current status of air quality in the building and baseline information on the factors that have a potential for causing problems in the future. For more information about developing and using an IAQ profile, see Module 8 – Creating an IAQ Profile.

NBC: National Building Code of Canada. NFC: National Fire Code of Canada.

Off-gassing: the production of gases from the chemical deterioration of a substance over time, and the release of gases from materials into the air. [See VOCs]

Pollutant pathways: avenues for distribution of pollutants in a building. HVAC systems are the primary pathways in most buildings; however all building components interact to affect how air movement dis- tributes pollutants.

Radon: radon is a colorless, odorless, radioactive gas that occurs naturally in the environment [from the breakdown of uranium in soils and rocks]. Outdoors, its concentration is rendered negligible. But when it is emitted into an enclosed space, such as a building, it can accumulate to high levels and be a carcino- gen. [Exposure to high levels of radon has been associated with an increased risk of lung cancer.] Radon can seep from the ground into buildings through cracks and unsealed penetrations in the floor and walls abutting the ground.

Atemluftfilter_EinwegmaskeVolatile organic compounds (VOCs): compounds that vaporize (become a gas) at room temperature. Common sources which may emit VOCs into indoor air include housekeeping and maintenance pro- ducts, and building and furnishing materials. In sufficient quantities, VOCs can cause eye, nose, and throat irritations, headaches, dizziness, visual disorders, memory impairment; some are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.

For a more complete list of terms, see http://www.epa.gov/iaq/glossary.html 

You can find this post, as well as more information in Module 1 – Introduction to Indoor Air Quality (IAQ) 

Share This: