Four Ps of IAQ

The Four Ps of IAQ

I’m not the first, second, or probably even the thirty-second person to write about improving indoor air quality problems using the four Ps approach. It’s a well-known thought process in the building science community—not sure if that’s the case in HVAC circles.

The first P is for pollutants. In this context, a pollutant is something that contaminates the air. It can be one or more of many things—mold, moisture, animal feces, and harsh chemicals are some of the more common ones in an average home. If you remove the pollutants, there is no longer an IAQ problem.

The next P is for pressure differential. If the pollutant cannot be removed, creating a pressure differential will prevent it from entering or spreading throughout the occupied area. But you already know this. That’s why you turn on the fan when going to the bathroom or the range hood while cooking.

Another P is for pathway. If there is a pollutant—with an unfavorable pressure differential—there still needs to be a pathway to the occupants for that pollutant to become an issue. Eliminate the pathway, and the pollutant can be contained.

The last P, but definitely not least, is for people. You’ve heard this before: if a tree falls in the middle of the woods, does it make a sound? Well, if there is a pollutant with a pathway and a pressure differential but no people, is it really an IAQ problem?

In short, it’s always best to deal with the source of the IAQ problem, but if you remove any one of the four “Ps,” there will be an air quality improvement.

—Neil Comparetto, Co-owner of Comparetto Comfort Solutions in Virginia

Related Tech Tips

Why Measuring Static First Isn't Always Productive
There is a big move in residential and light commercial HVAC toward measuring static pressure regularly during commissioning, service, and maintenance. Don't get me wrong… Measuring static pressure is VERY important. The challenge comes in when techs begin taking measurements without understanding where to take them, what they mean, or worse: they use measurements as […]
Read more
Aftermarket Motor Selection & Considerations
This article was written by technician and HVAC School community star Kenneth Casebier. Thanks, Kenneth! When looking at replacing a single-phase A/C motor with an aftermarket motor from your van, there are a few things you should know and pay attention to. First, the factory OEM motor will always be the best option, especially when […]
Read more
Zeroth Law of Thermodynamics
Zeroth? ZEROTH? is that even a word? Apparently so, because… SCIENCE. The zeroth law of thermodynamics establishes the relationship between multiple objects and a common state of balance between them. It is sometimes called the law of thermal equilibrium. Heat always tries to find a state of balance. “Hotter” is a relative term, but an […]
Read more

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from