Over the years I have had about twenty articles published in The Synergist, a great honor for me. I’ve received many compliments, comments, and questions about these articles. One early comment that made me a little nervous was, “How come you write so much technical stuff? I had a hard time understanding how to use your Figure 2.” Those kinds of questions made me try to better explain figures, tables, and graphs that may be new to readers.

Another question was related to why we cover so much ventilation in these articles. Well, for one reason, that is my specialty, having graduated as a mechanical engineer in college before getting a graduate degree in OEHS at the University of Michigan. I have combined the two throughout my long career. Plus, of course, good clean air and ventilation are keys to a healthy environment.

This article returns to some of the fundamental factors associated with OEHS and ventilation. How and why are they related? Let's start with some fundamentals.

VENTILATION BASICS Ventilation is used to provide comfortable, healthy, and safe environments for workers and building occupants. But invariably, something goes wrong with many ventilation systems. IHs are often expected to find potential problems and suggest corrections. We often call this work “problem solving” or “troubleshooting.”

These terms are also thought of as subcategories of an “investigation.” So, our work may be the first “screening study” in a larger investigation carried out by others. Our work is also usually an individual effort over a relatively short time, whereas investigations may involve many people and extensive efforts over a longer period of time.

Troubleshooting usually involves three phases of study: characterizing complaints and gathering background data, checking the performance of ventilation systems and their controls, and measuring carbon dioxide. We often gather the data ourselves, or our coworkers gather it for us.

When troubleshooting, we first look for the obvious—that is, the simple explanation. “Hoofbeats suggest horses, not zebras,” is often a good rule of thumb.

Initially, we usually talk to those who are complaining. After we understand the problem and gather the background data we feel we need, we then look for obvious sources of the trouble.

The causes of complaints can be problems inside the building or from the outside environment. We also usually look for chemical issues, microbiological problems, or malfunctioning equipment, for example.

When the issue is primarily related to IAQ problems, we usually find the ventilation system is involved. Most complaints usually stem from: • temperature or humidity extremes • insufficient outdoor air (OA) being introduced to the system • poor distribution or stratification of supply air in the occupied spaces • poor maintenance of HVAC equipment • prioritization of energy conservation over human comfort or health • stuffiness (inadequate or improper air delivery) • draftiness (too much supply air or improper terminal settings) • improper pressure differences (for example, doors are hard to open or close because of high air pressure at the door) • poor air filtration (for example, dirt, bugs, or pollen in the air duct delivery system) • settled water in the HVAC system • visual evidence of slime or mold in the ventilation system or occupied space • improper balance of the air duct distribution system • air dampers at incorrect positions (because of adjustment by occupants, for example) • variable air volume (VAV) ventilation systems in non-delivery or low-delivery mode

CORRECTING PROBLEMS After we have determined the potential sources of these issues, we start to identify possible causes and provide fixes, sometimes with the help of specialists such as ventilation engineers. For example, if an occupant complains about stuffiness or odors, we determine whether the cause of the problem is insufficient fresh OA; if it is, then we or our specialists can potentially solve the problem by providing OA at the amounts recommended by ventilation experts or in recognized standards.

If you think you have identified one or more of the problems listed above, don't overreact. These are probably not life-threatening situations. Correcting the problems may not completely satisfy those who are registering complaints. Corrective measures can't hurt, of course, and any attempts to solve the problem will probably be appreciated. One fact about IAQ complaints is that identifying all contributing sources, causes, or agents can be difficult.

As mentioned above, we almost always measure the carbon dioxide levels. Concentrations exceeding 800–900 ppm can suggest the potential for complaints. Concentrations above 1,000–1,200 ppm might suggest too little outdoor air and the potential buildup of airborne contaminants sufficient to raise complaints.

Carbon dioxide concentrations are typically four to five percent of exhaled breath, so be sure not to sample or measure carbon dioxide too close to the breathing zone. Rather, take the samples in the general areas of the room or somewhere close to where the complaints are being generated. Measurements are best obtained near lunch and quitting time, when concentrations are likely to be near their maximums. Also, be sure to measure the outside concentration of carbon dioxide.