Guide to Indoor Air Quality

With the one-year anniversary of COVID-19 coming up, many of us have spent much of the last year thinking about our risk of exposure to the virus. More specifically, this has more of us thinking about airborne contaminants – and their potentially hazardous effects – than ever before. For many of us, those concerns are particularly troublesome when it comes to indoor air quality (“IAQ” for short).

This is for two good reasons. First, we spend much of our time in doors (up to 90% for the average American, by some estimates). Second, dangerous airborne particles are present much more frequently – and in greater numbers – indoors.

While some of us are thinking about airborne contaminants for the first time, others know all too well, as some of the most common particles are responsible for triggering allergies, asthma, and can also be problematic for those that are especially sensitive to volatile organic compounds (“VOCs”).

In this article we’ll take a look at the main airborne particles that are problematic for homeowners and understand the differences between them. We’ll then talk about the main ways to keep the air inside your home pure and free of any contaminants.

The Source of it all: Particle Matter

When thinking about indoor air quality, the first term to get familiar with is particle matter. Particle matter refers to the microscopic pollutants that circulate in the air in your home. While all particle matter is microscopic, it’s not all created equal from an IAQ perspective. One indicator of the potential danger from a particular type of particle matter is its size. Your first guess might be that larger particle matter is more dangerous, but you’d be wrong! It’s actually the smaller forms of particle matter (generally considered to be 10 microns in diameter of smaller) that have the most potential to be inhaled deep into the lungs and cause problems.

Particle matter is around us almost constantly indoors, whether or not we’re aware of it. Common sources include organic particle matter that traveled from outside (such as pollen and mold spores). Cooking, cleaning supplies, candles, and other common household activities can also release pollutants into the air.

Another important distinction is that these pollutants can either come in a solid form (like the example of pollen above), or a gaseous form (such as cigarette smoke). That distinction will be important later!

Ways to Improve Your Indoor Air Quality

While there’s no shortage of technology out there promising all-in-one solutions for your IAQ needs, the fundamentals of IAQ have been well established by the US Environmental Protection Agency (“EPA”). They are: ventilation, filtration, and humidity control.

Let’s take a look at each one in more detail.


Simply put, the idea behind improving the ventilation throughout your home is that introducing outdoor to the home’s interior significantly dilutes the concentration of particle matter.

The specific way this concentration is measured by professionals is the density of particles in a cubic meter of air within the home. There are specialized tools to measure this, but for our purposes just keep in mind that for the most part the number one things you can do to improve your IAQ is to make a conscious effort to ventilate your home!

Many homeowners think they’re doing this automatically when they run their home’s AC or furnace, but this is a common misconception. The vast majority of modern HVAC equipment does not take in fresh air when it runs – it simply recirculates air from the home’s interior.

Another thing to keep in mind about ventilation is that it becomes critical when you’re performing activities that generate particle matter, such as cooking or cleaning. So, next time you have something on the stovetop, be sure to crack a nearby window and feel the difference!


The second component of indoor air quality is filtration. Broadly speaking, this means the use of a device to help remove particle matter from the air once it’s already been introduced into the home, either as a standalone device or part of the home’s broader HVAC system.

This might sound like a hassle, but many homeowners (those who have a gas furnace in the home), already have all they need! Gas furnaces have a replaceable filter next to the furnace inserted in the ductwork, and if it’s been a while since you replaced your filter, you aren’t getting the most out of it!

To check your filter, simply locate the filter near the furnace, power the furnace off and pull the filter to remove it. Some filters are single-use, and need to be thrown out and replaced with each use.

If you’re a YardYum reader, chances are you like to think about your environmental footprint. If that sounds like you, reusable furnace filters, which are washed instead of discarded after each use, are a cost-effective option that reduces waste as well.

If you’re already making the most of your home’ HVAC system and are ready to take the next step, a standalone air purifier can make a big difference.

Air purifiers have become increasingly popular in recent years, and with so many options on the market, it can be difficult to know what to choose. Remember the distinction of solid particle pollutants, like pollen, and gaseous pollutants, like smoke, before? Which of those two pollutants you most want to eliminate will tell you all you need to know about what type of air purifier to get.

If your concern is primarily pollen, mold spares and other solid particle matter, you’ll want to ensure you have an air purifier with a True HEPA filter. HEPA stands for “High Efficiency Particle Air [filter]” and is the gold standard for particle filtration on the market today. Conversely, if the source of your concerns is a gas such as cigarette smoke, you’ll want to make sure you have a purifier with an activated charcoal (also referred to as “activated carbon”) filter, as these are designed for gaseous air pollutants.

Humidity Control

The last component of IAQ control, humidity, is the one that’s most often overlooked. You might be surprised to hear that excess indoor humidity can increase concentrations of certain indoor air pollutants, including mold. As we’ve alluded to already, mold, if permitted to grow, produces microscopic mold spores that can be inhaled and cause respiratory problems.

For those who are less familiar, it can be difficult to get a sense for the appropriate amount of humidity in the home. For that reason, hardware stores sell devices known as humidity gauges that can tell you how humid your home is. According to the EPA, indoor humidity between 30 and 50 percent is the sweet spot.

Hopefully you now have a good understanding of common indoor air pollutants and the best ways to keep them out of your home. Try the suggestions in this article, notice the difference, and breathe easy!

Posted in Homeowners on Mar 11, 2021


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