Until recently, I was blissfully breathing, unaware of the microscopic particles — the dust mites, dander, pollen, mold, viruses, pet smells, germs, cooking odors, twelfth-hand smoke and who knows what else — lurking under my nose. Then, as I was researching last week’s column, in which I dusted up a fuss about pet fur and shared ways to bust the fuzz covering our furniture, floors and clothes, that changed.

The problem with this job is that I can’t un-know what I now know.

As I looked for ways to combat the unwelcome evidence of our pets — including their, ahem, smell — I almost stopped breathing as I discovered what all hung in our homes’ air.

So much for breathing easy.

To keep a clean, odor-free home while living with pets, all indicators point to the benefits of an in-home air purifier. Dubious about whether these systems make a difference and wary of falling into an emperor-has-no-clothes trap, I dug deeper.

I searched the Environmental Protection Agency website and found evidence that air purifiers are nothing at which to sniff. To improve indoor air quality, the EPA recommends a three-step approach: First, remove pollutants and their source. Second, ventilate rooms by letting outside air inside. Third, use air filtration.

Specifically, that means either running a portable air purifier, which filters the air in a single room or area, or upgrading the air filter in your central HVAC (heating, ventilation and air-conditioning) system. Both purifying methods can measurably reduce indoor air pollution, according to the EPA.

I decided to bring home a portable air purifier. Worst that could happen was nothing. But maybe it would alleviate my morning sniffles, clean my home of pet smells and banish other indoor pollutants such as dust, dander, pollen, viruses, cooking odors and mold.

A week after letting the unit run in different rooms — kitchen, office, bedroom — I checked the filter. Though I can’t see the invisible, what I could see was a light film of dust, fuzzy pet dander and several mosquitoes. My husband, an even bigger skeptic, said he was sneezing a lot less.

Convinced that this little box, about the size of a small printer, was pulling its weight, I called Rabbit Air, a company based in Downey, Calif., that has been making portable air purifiers, including the A3 model I got, for 20 years. Company spokesman Ryan Smith fielded my questions.

Question: Since most of what air purifiers filter are particles far too small to see, how can we know if a system is working?

Answer: The main way is you will feel a difference in the air right away. It will smell cleaner. You’ll notice a lack of odors. Second, you’ll be able to tell by looking at the first filter, which you should clean every few months. (These are washable and reusable.) The first of several filters in the system, this offers visible proof. After a while, it looks like a vacuum bag, then you realize that could have been your lungs.

Q: How do portable air purifiers differ from systems that work directly with the central HVAC?

A: Both purify the air. Portable units mainly work on the room you have them in. You can move them room to room like a space heater. A central system will increase air quality throughout the house but is not as targeted.

Q: Which households need air purifiers most?

A: Every house can benefit, but our typical customers fall into three categories: those who struggle with allergies and asthma, homes that have a smoker, and pet owners, including homes with large birds, which create lots of dander. Homeowners in areas prone to fires also appreciate that purifiers will clean indoor air of smoke.

Q: Is it OK to open a window or door when the unit is on?

A: I recommend it. Outdoor air quality is often two to 100 times better than indoor air. However, you might want to first check the air quality and pollen count in your area. If pollen count is high, you’ll want to keep windows closed.

Q: Where is the best place to park a portable purifier?

A: One rule is to put it as close to the source of pollution as possible, like, say, the kitchen, if you have cooking odors. Another rule is to put it as close to you as possible, so by your desk when you’re working, or by your bed while you sleep.

Q: When choosing an air purifying system, what should you look for?

A: You want to make sure the system uses a HEPA filter, which stands for “high efficiency particulate air.” Around since World War II, HEPA filters are the gold standard in air purification and will catch particles as small as 0.3 microns with 99.97% efficiency, as well as airborne bacteria and viruses, pet allergens, mold spores, bacteria, dust mites, VOCs (volatile organic compounds) from new carpet, and smoke.

Also check the system’s clean air delivery rate. This is the number of air changes per hour, or how fast the unit cleans all the air in a given space when set at its highest fan speed. You also want to look at the unit’s coverage area. Our largest unit, the Rabbit Air A3, covers 1,070 square feet with two air changes per hour, or one every 30 minutes. Choose a system that is a good fit for your space. The stronger the purifier and the larger capacity, the higher the price point.

Marni Jameson is the author of seven home improvement books. Reach her at marnijameson.com.