Indoor Air Quality – What it is & why you should care

indoor air qualityIndoor air quality has been around forever, but just like everything else us bonehead humans didn’t start paying attention to it until recently. Indoor air quality is technical, fickle, and in general a pain in the behind.

It is necessary. As a building engineer or homeowner, it’s important to at least have a handle on what’s going on both at home and at work. Are you like me and burn a lot of wood in a fireplace? Our indoor air quality is lower than someone that doesn’t. We need to take extra care in ventilating our
home. Feel me?

What is Indoor Air Quality?

iaqIndoor air quality, the technical definition from OSHA, describes how inside air can affect a person’s health, comfort, and ability to work. It can include temperature, humidity, lack of outside air due to poor ventilation, mold growth from moisture, or perhaps exposure to other chemicals.

Indoor air quality, in regular terms, is like a collective measurement of the quality of air people are breathing mainly at work but at home too. Building engineers can control and monitor the quality of air you get when you are at work. Concern with indoor air quality really seemed to take off around 2000, along with that construction boom and buildings and tenants have been keeping up.

For the past several years, there has been debate among indoor air quality specialists about the proper definition of indoor air quality and specifically what constitutes an acceptable indoor air environment.

Why Care About Indoor Air Quality?

The quality of indoor air inside buildings, homes, offices, schools, and other workplaces is important not only for comfort but also for health.

Poor indoor air quality has been tied to a variety of symptoms, many of which don’t make our jobs as building engineers any easier – headaches, fatigue, and irritation of the eyes, nose, throat and lungs. In addition, some specific diseases have been linked to air contaminants or low indoor air quality environments, like asthma with damp indoor conditions. In addition, exposure to things like asbestos and radon, don’t necessarily cause immediate symptoms but could potentially lead to cancer later on. But seriously, what doesn’t? Rimshot.

Factors Affecting Indoor Air Quality

indoor air quality concern

Potential IAQ issue – dirty coil.

Many factors affect indoor air quality. These factors include poor ventilation such as a lack of fresh, make-up outside air, temperature control issues, high or low humidity, perhaps a recent remodeling that created a lot of dust, and other activities in or near a building that can affect the fresh air coming into the building. For example, maybe a construction crew is paving the street. The air handling units trying to introduce some fresh air into the building may catch a whiff of the tar. Now you’re breathing it.

Sometimes, specific contaminants like dust from construction or renovation, mold, cleaning supplies, pesticides, or other airborne chemicals, even tiny amounts, released as a gas over time as they evaporate may cause poor IAQ.

Yes, the perfume Doris wears in HR is considered a pollutant.

At home, indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems. Inadequate ventilation, even a simple clogged filter (I’ll get that next week right?), can increase indoor pollutant levels by not bringing in enough outdoor air to dilute the bad stuff being emitted from the indoor sources but also by not escorting these indoor air pollutants out of the home or into a filtration system.

Good Indoor Air Quality?

The qualities of good IAQ should include comfortable temperature and humidity set points, an adequate supply of fresh outdoor air, and control of pollutants from the inside and outside.

The How of Indoor Air Quality

The right ventilation system along with a good building maintenance program can prevent and fix IAQ problems.

Surprisingly OSHA does not have IAQ standards, it does have standards about both the ventilation and on some of the air contaminants that can be involved with indoor air quality problems.

Some states, well two, california and New Jersey, already have state specific indoor air quality guidelines and regulations apparently. If more states haven’t been added by now, they will be. Eventually it will probably have to even become global! Or is it already happening?

indoor air quality what is it

Pretty clean.

In the UK, for example, classrooms are required to have 2.5 outdoor air changes per hour. This means that the HVAC system is supposed to exchange enough inside air with outside air with enough volume to fill the classroom 2.5x. If the room is 1000 cubic feet in size, the HVAC needs to deliver 2500 cubic feet of outside air per hour. Fresh air for the baby student brains.

Building owners and concerned home builders take IAQ into account when designing the HVAC system. Seen it firsthand.

Modern building planners now use demand controlled ventilation when possible and where feasible. Let’s use parking garages as an example. They are carbon monoxide storage sheds right? All of those cars in and out of them all day. The carbon monoxide piles up and piles up.

They used to have exhaust fans that would simply run continuously. What happens to parking garages at night? Traffic goes to zero, no carbon monoxide production. There was no need to have any exhaust fan running, let alone all of them. So, rather than having them run at a fixed air replacement rate or even more simply, all of the time, carbon monoxide sensors were added to control the rate dynamically, based on the emissions of actual vehicles. If the sensors didn’t “feel” high enough CO levels, they provided no electricity to the fans. Pretty smart.

Moisture management along with humidity control requires that we operate HVAC systems as close to design criteria as possible. Trying to wrangle with both moisture and humidity, especially to control IAQ issues, may sometimes conflict with optimization efforts to conserve energy.

For example, trying to control moisture and humidity requires systems to supply make-up air at lower temperatures, instead of the higher temperatures sometimes used to conserve energy. However, for most of the US and many parts of Europe and Japan, outdoor air temperatures are cool enough most of the time that the air does not need much further cooling to provide thermal comfort.

However, high humidity conditions create the need for attention to humidity levels indoors. High humidities give rise to mold growth, moisture indoors is associated with more respiratory problems.

Indoor Air Quality Guide
indoor air quality guide

Free IAQ Guide from ASHRAE

Check this out. Doing research for this post I found this free IAQ guide from ASHRAE that you can download. It appears to be free. Probably more information, checklists, troubleshooting.


Everyone should be pretty well up to speed on indoor air quality and at least be able to explain it and why we care about it. The quality of air that someone is continuously inhaling and exhaling throughout
their day greatly impacts their overall health and can have lasting effects. You want to make sure that you are getting as clean and as fresh air as possible as much as possible.

If you’ve got any questions, use the comment form below. If you’re shy, go ahead and email the site. Stay tuned for the next installment.


My brain.
Wikipedia – Indoor Air Quality

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