THE COHEN GROUP
  Environmental Health & Safety Consulting Services

The Cohen Group Newsletter - Volume 6  Issue 2, Article 4,  April, 2004

 Indoor Air Quality – A Comprehensive Approach

Julie V. Wellings, CIH

We are frequently asked by our clients to investigate and help resolve indoor air quality (IAQ) concerns. But just what is "indoor air quality"? And what building conditions and other factors may influence air quality and an occupant’s perception of air quality?

The U.S. EPA (in EPA/400/1-91/033) describes a "healthy indoor environment" as one in which "the surroundings contribute to productivity, comfort and a sense of health and well being" and identifies air quality as one component of that environment. "Good indoor air quality" is defined as that which would result from (1) adequate ventilation, (2) control of airborne contaminants and (3) maintenance of acceptable temperature and relative humidity. All of these factors may interact to result in "good", "fair" or "poor" indoor air quality, whether determined by measurements and air sampling or as perceived by building occupants.

We generally recommend a two-phase approach to indoor air quality investigation. The first phase will be a "preliminary" investigation including inspection, interviews, and direct-reading measurement of general IAQ indicators. Where a suspected source of contaminants has previously been identified, the first phase may also include air sampling for one or more suspected contaminants. Generally, however, sampling for airborne contaminants (if suspected) will be performed in a second-phase investigation, which may also include additional inspection, interviews and direct-read measurements. As an example, we offer the following "case study" summarizing a recent IAQ survey performed by The Cohen Group:

Occupants of a small medical office, located within a large office building, reported that they experienced sinus congestion and headaches when working in the office suite. The building manager indicated that occupants were particularly concerned about possible airborne mold and had previously been dissatisfied with temperature and air movement in the suite.

Upon arriving at the suite, we interviewed the occupants and confirmed the nature of their concerns. We then met with the building mechanical contractor and reviewed the configuration and operation of the suite’s ventilation system. Next, we inspected the suite interior, above-ceiling space, ventilation system components and surrounding environment. Concurrently, we conducted direct-read measurements for indoor air quality indicators including carbon dioxide, carbon monoxide, temperature and humidity. Then, to address the occupant’s previously stated concern, we conducted air sampling for mold particulate.

Our direct-read measurements indicated that indoor temperature, humidity and carbon dioxide/carbon monoxide levels were all within normal, acceptable ranges. No visible evidence of mold growth was observed and air sampling for mold particulate indicated that indoor mold levels were similar to or lower than outdoor levels. However, we did identify two conditions that were likely affecting indoor air quality in the suite.

First, occupants had re-set the local thermostats, reportedly to minimize the occurrence of "drafts" within the space. However, this action also reduced the amount of outside air provided by the ventilation system. Second, a semi-volatile chemical with a low irritation threshold (but high odor threshold) was used in the space without the benefit of local exhaust ventilation. While carbon dioxide readings indicated that the existing ventilation was sufficient for normal building contaminants, it was determined that irritant chemical vapors were likely becoming concentrated in the space.

Our recommendations for further action included (1) adjustment of thermostat settings so that additional outside air would be provided to the space, (2) adjustment of air supply diffusers to minimize "drafts" at occupant work stations, and (3) installation of a local exhaust hood at an existing ventilation flue to allow removal of irritant chemical vapors at their source. We also recommended air sampling to evaluate airborne chemical concentrations both prior to and following ventilation system modifications. The building manager later reported that, upon implementation of our recommendations, the IAQ problem had been resolved.

Please call if you would like to discuss IAQ concerns, investigation protocols and/or potential resolutions.