Legend Technical Services

Indoor Environmental Quality


Air quality inside a building is never exactly like what is encountered in the outdoors.  HVAC systems supply comfort temperatures more in line with human needs and nuisance particulate like PM10 and 2.5 are filtered out from the outdoor air.  HVAC systems are designed to provide human comfort by moving air around the building and distributing replacement outside air.   Finishes are chosen and installed to minimize impact to air quality.  Relative humidity levels may or may not be optimum for human comfort but are maintained below 50% during the cooling season and at a minimum of 30% during the heating season.  


Air quality that is acceptable to 95% of the occupants is considered acceptable air quality.  What of the other 5% that perceive poor air quality in their workspace?  Are these people just too demanding?  Too sensitive?

Some people have greater sensitivities to different air quality contaminants (for example molds, fine fiberglass particles, or odors).  Their location in the building may be causing them to receive a greater burden of air contaminants than others.  The building ventilation system may be configured creating higher contaminant loads in some locations or less outside air in other spots or insufficient heating and/or cooling because of heat generating equipment, windows, etc.   A process may be going on near them that creates air contaminants.  Bottom line is that the 5% “complainers” may have valid concerns that need investigation.


Air quality complaints are rarely investigated at outset. In the beginning, there is hope that it is a short-term problem that will resolve on its own.   Concerns are frequently raised to building facilities personnel for an extended period of time before outside agencies become involved in determining whether there are issues contributing to poor air quality, characterizing the poor air quality through testing, and coming up with a plan to improve air quality.

So, what should YOU, as the building responsible party, do to prepare for an investigation?

Have a copy of the HVAC plans.  Most issues have their root cause in the HVAC or its operation and an understanding of the system is important in the investigation.

Gather building occupant complaints. Analysis of the specifics of complaints is important – particularly if complaints from early on were preserved in written form.  An understanding of the timing is particularly relevant if periodic odor is an issue.

Changes in building occupancy/wall configuration, etc.  Sometimes changes are made in the building which have not considered the operation of the HVAC system.  Sometimes supplies and returns are separated by walls.  Sometimes supplies or returns are eliminated.  Sometimes contaminant generating processes are added without considering the location limitations.


Investigating indoor air quality is a phased process.  The process starts out by first understanding the building systems and the occupant complaints and then developing a plan to test.  Testing may need to be done at certain times (for example when an odor is occurring) so that we can best capture “worst case” for the problems.   Air quality complaints can occasionally be attributed to one contaminant and one process making that contaminant airborne but that is rarely the case.  More probable is a combination of events triggering air quality problems with no discernable causal contaminant.  Many of these contaminants will be at very low levels and need to be at their highest levels to both detect and quantify.

Investigations frequently center on identifying a contaminant(s) that is above exposure limits.  This is not a good approach for two reasons: 1) exposure limit development has not kept up with newer chemical technology and emerging contaminants so it is difficult to assess exposure and 2) it is seldom a single contaminant or combination of contaminants causing issues with the exception of odor problems.  Even with odor problems, many of the most odorous compounds are nitrogen and sulfur containing chemicals, react rapidly, and are difficult to collect and identify.  In many cases, identifying a causal agent to an odor and an understanding of the components of various types of odors is a more cost-effective approach to actually identifying the components of the odor.  

A “wholistic” approach to indoor air quality investigation is more likely to produce factors that impact air quality that can be addressed without identifying a causative contaminant(s). 


LEGEND has expertise in review of building mechanical systems to identify areas where indoor air quality might not be optimum and tailor the investigation to those areas as well as areas of identified as problematic through complaints.  LEGEND has the following expertise:

·         Mechanical plan review to identify potential areas where IAQ concerns could occur

·         Measurement of selective systems for air flow

·         Pressure differential measurements

·         Continuous monitoring of IAQ parameters such as carbon dioxide, carbon monoxide, temperature, and relative humidity to identify patterns in the data

·         Time weighted average (TWA) or grab sampling to identify and quantify contaminants present in the air

·         Microbial assessments including fungi, yeast, bacteria, and PCR for fungi associated with water intrusion

·         Reports that explain data and identify solutions

Contact us

For further information contact:

Cheryl A Sykora,CIH,CSP,CHMM,SDSRP – [email protected]  612-619-6547

Keith Giorgi – [email protected], 651-238-0543