Indoor Air Quality Assessment – Technical Approach

Indoor air quality has become a major issue due to recent conservation efforts to reduce the cost of heating and cooling buildings, increased reliance on mechanical ventilation equipment, and growing awareness that air quality problems can impact the health, comfort, and productivity of building occupants. Since 1974, in the wake of the first oil embargo, the need to reduce building maintenance and operation costs has been a priority of building managers. To reduce these costs, new buildings have been constructed as hermetically sealed structures. Additionally, older buildings have been sealed by the addition of energy-efficient window and door closures. As a result, fresh air ventilation is provided primarily by way of mechanical air-handling equipment.

The energy savings have frequently been realized at the cost of reduced air quality. Inadequate fresh air ventilation has caused the products of human respiration, chemical off-gassing and biological contamination in buildings to accumulate. Some of the chemical species include carbon monoxide, various volatile organics, and formaldehyde. Often, the impact of chemical concentration increase is exacerbated by temperature effects, especially when temperature control is unable to maintain thermal parameters within the thermal comfort ranges established by ASHRAE Standard 55-1981.

Air quality complaints frequently are generated by inadequate ventilation, which is a commonly encountered condition. Renovation projects over the years may have dramatically altered air flow characteristics of the spaces, and ductwork may have been substantially modified. Maintenance schedules of the heating, ventilation and air conditioning (HV/AC) units may have been irregular, affecting the design performance of the units. Finally, casual housekeeping of the air handlers may have resulted in conditions conducive to microbiological contamination. All of these elements can have a significant impact on the quality of indoor air.

In many ways, the evaluation of indoor air quality complaints becomes a Sherlock Holmes style investigation into esoteric clues and vague physical symptoms. Often the complaints involve issues that have nothing to do with air quality.

The investigator must learn to decipher the evidence and glean the kernel of truth from data that often sounds like this:

I was sick, sick unto death. The walls of my cubicle closed in around me, and my skin crawled. I gasped for breath, but the air had grown thin and unreliable. I was drowning. I could not stop the swarms of ethereal invaders from teaming out of the ducts. I choked as the awful chemistry of destruction entered my lungs. I was helpless in their presence.

It takes a seasoned pro to make sense of these stories, and to determine if an irregularity in the building or its operation is at play. Read on to learn how an experienced hand gathers clues.