Breathing easier through proper air filtration

Odors and gaseous contaminants can permeate throughout your facility, leading to a variety of potentially bad health effects for patients as well as less-than-ideal working conditions for employees. One problem is that the traditional air filters used in institutional buildings capture particulate contamination, but do nothing to reduce gases.

Not all gaseous contaminants, including volatile organic compounds (VOCs), can be identified by smell alone. In fact, the issue of controlling VOCs and other gaseous contaminants may be even more important when there are no odors associated with them to trigger complaints.

Fortunately, most harmful gaseous contaminants can be removed from the breathing air inside buildings with a combination of source removal/reduction, proper ventilation, and an effective gas phase air filtration system.

Gaseous Contaminants and Their Health Effects

Common gaseous contaminants in institutional buildings may include combustion by-products, such as carbon monoxide, nitrogen oxides, sulfur dioxide, and polycyclic aromatic hydrocarbons (PAHs); human and cooking odors; and carbon dioxide and VOCs (which are emitted as gases from certain solids or liquids.)

According to the U.S. Environmental Protection Agency (EPA), concentrations of many VOCs are two to five times higher indoors than outdoors, and elevated concentrations can persist in the air long after the generative activity is completed.

A variety of different VOCs may be in the indoor air at any one time. They are emitted by a wide range of products commonly found in institutional facilities, such as:

  • Paints and lacquers

  • Paint strippers

  • Cleaning supplies

  • Pesticides

  • Building materials and furnishings

  • Office equipment such as copiers and printers

  • Graphics and craft materials, including glues and adhesives

  • Permanent markers

According to the EPA, research shows that some VOCs can cause chronic and acute health effects at high concentrations, and some are known carcinogens. Low-to-moderate levels of multiple VOCs may also produce acute reactions, for example:

  • Eye, nose, and throat irritation

  • Headaches

  • Loss of coordination

  • Nausea

  • Fatigue

  • Liver, kidney, and nervous system damage

  • Allergic skin reactions

These effects can be a drain on employee productivity, may lead to increased employee absenteeism, and may even result in additional medical costs for employees and residents/patients alike.

Source Reduction and Removal

Pollutant source removal or reduction is an effective approach to resolving indoor air quality (IAQ) problems related to gaseous contaminants when sources are known and control is feasible. When source removal is not possible or practical, there are a number of steps that can be taken to reduce the amount of odors, VOCs, and gaseous contaminants in the indoor environment:

  • Safely discard partially full containers of old or unneeded chemicals. Gases can leak even from closed containers.

  • Buy limited quantities of VOC-emitting products that are used only occasionally or seasonally.

  • Use sealants on all exposed surfaces of paneling and other furnishings.

  • Allow time for building materials in new or remodeled areas to off-gas pollutants before occupancy.

  • Adopt integrated pest management techniques to reduce the need for pesticides.

  • Store food properly and dispose of garbage promptly.

  • Select or specify low-emitting products when building or remodeling.


One technique for controlling odors and gaseous contaminants is to dilute them with outdoor air. Dilution can only work, however, if there is a consistent and appropriate flow of supply air that mixes effectively with room air, according to the EPA. To help achieve acceptable IAQ while minimizing energy consumption, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has a ventilation standard (62-1989) to provide a minimum of 15 cfm of outdoor air per person (20 cfm/person in office spaces.)

Another technique is to use dedicated exhaust ventilation systems to isolate and remove contaminants by maintaining negative pressure in the area around the contaminant source. Local exhaust can be linked to the operation of a particular piece of equipment (such as a kitchen range) or used to treat an entire room (such as a restroom or custodial closet).

Avoid recirculating air from areas that are strong sources of contaminants. Confine activities that produce odors and gaseous contaminants to locations that are maintained under negative pressure relative to adjacent areas. Finally, make sure that external vents are located well away from the fresh air intake of the HVAC system to avoid recontamination.

Gas Phase Air Filtration

Air cleaning, via air filtration, is usually most effective when used in conjunction with either source control or ventilation. However, filtration may be the only approach when the source of pollution is outside the building and the gaseous contaminants are brought in through the building’s fresh air ventilation system.

Controlling gaseous pollutants requires specialized air filtration products. Traditional particulate air filters—even HEPA filters—are not effective at removing gaseous contaminants.

Most gas phase air filters are made with activated carbon. On a microscopic level, activated carbon looks and acts much like a natural sponge, with highly porous particles that have a vast amount of surface area. Carbon-based odor molecules have a high affinity for bonding with the activated carbon because it lowers overall surface energy. As odor molecules come into contact with the carbon, they are drawn into the carbon and held in place. Of all the adsorbents known, activated carbon is one of the strongest physical adsorbents, so it is an excellent material for creating and maintaining a fresh and clean-smelling environment.

Some filters with activated carbon are dual-layer filters. The upstream layer provides particulate filtration and protects the carbon layer from particulate loading to ensure maximum odor removal. The downstream layer absorbs and retains gaseous contaminants from the air stream.

Gas phase filtration may be recommended in any of the following scenarios:

  • Newly constructed buildings

  • Newly remodeled buildings (with new wallpaper, paint, carpets)

  • Newly installed furnishings

  • Areas where large volumes of photocopying are conducted

  • Areas where known solvents are used (laboratories, nail salons, spas)

  • When source control and ventilation control have not resolved odor issues

  • When building occupants complain of eye and respiratory irritation

In addition, ASHRAE’s Ventilation Standard 62-1989 has a provision to reduce the amount of ventilation air required in a building if effective gas phase filtration is employed. This may be an opportunity to reduce a building’s heating and cooling costs as well.

When gaseous contaminant filtration is indicated, effective filtration systems employ a combination of particulate and gas phase filtration technologies. In two-stage HVAC filtration systems, particulate pre-filters in the MERV 7 to 8 range protect higher efficiency final filters. In environments with significant gaseous contaminant levels, final filters may be replaced with granular bed or deep pleat carbon filters. If this is elected, it’s important that the HVAC system has adequate fan capacity to handle the increased airflow restriction of these filters.

In more typical scenarios, gaseous contaminant levels are low to moderate, and single-stage pleated gas phase filters may be used. These filters are more expensive than traditional pleated filters, but they remove the entire spectrum of airborne contaminants—particulates and gases. Be sure to select a filter that has a particulate filtration level of at least MERV 7, and again, be sure that the HVAC system has adequate fan capacity.

Beware of Silent Invaders

While the human nose is a good barometer for odor problems, it is important to remember that there are many gaseous contaminants present in institutional buildings that don’t generate odors. These gaseous contaminants should be removed from the breathable air inside buildings through a combination of source control, ventilation, and gas phase air filtration. Combined with effective particulate air filtration, gas phase air filters can help achieve superior IAQ, making your facility a healthier, more productive place for residents and employees alike.

Ronald Cox, CAFS, is Marketing Manager, Kimberly-Clark Filtration Products. For further information, e-mail or visit

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Topics: Articles , Facility management , Operations