How long does an air purifier need to clean a room?

Have you ever heard it said, “A woman’s work is never done”? Your air purifier is also never made. There are six basic reasons why you need to continually clean your air. Understanding each of them will help you get the clean air results you want.

Every now and then it’s never enough

The most common misconception about cleaning the air is the belief that it is a single task that once completed is completed until another day. Cleaning the air is not like vacuuming the floor, washing dishes or clothes. Using an air purifier for a few hours doesn’t finish the job of cleaning the air.

The reason is simple. Indoor air is constantly changing. Particles, gases, and microorganisms are constantly being introduced by things like foot traffic, coughing and sneezing, the normal shedding of skin (dander) from humans and pets, your central heating and air system, and other activities.

Six Facts About Getting Healthy Air

You most likely want specific health benefits, such as allergy or asthma relief. What do you need to know to make sure your air purifier delivers those health benefits? Consider the following six problems:

• Your personal sensitivity
• Pollutant dilution
• Pollutant dispersion
• Reintroduction of pollutants
• Air changes per hour (ACH)
• Efficiency level of your air purifier

How do these points relate to your air cleaning effort?

Each person has their own “turning point.” Environmental and personal health factors make it a moving target. Certain allergens can cause a reaction today, but not tomorrow. It depends on your total load of irritants and physical stresses.

The goal of air cleaning is to progressively dilute pollutants with clean air, keeping them below the threshold at which they react.

Why am I talking about dilution of pollutants and not total elimination? Because particles and gases don’t stop for an air purifier to capture one by one. The normal movement of the particles disperses them equally in the air in the room.

This means that the clean air coming out of your air purifier is almost immediately recontaminated by raw air. It cannot hold clean air on one side of the room while cleaning the air on the other side.

That is why your air purifier must run continuously. Constant treatment reduces contaminants and keeps them low.

Counteracting the cleanliness of the air is the reintroduction of new pollutants. Reintroduction is like an escape in a boat. Over time, the ship sinks. Air quality will also decline if you do not anticipate the rate of reintroduction of new pollutants.

Just as the boat needs constant bilge to stay afloat, the air in the room needs continuous cleaning to stay healthy.

This is where ACH, or hourly air changes, comes into play. ACH indicates how quickly you can rescue pollutants from the air in your room.

ACH is determined by dividing the cubic feet of clean air your air purifier can deliver in an hour by the cubic feet in the room. Let’s say your room is 12 x 15 with a ceiling of eight feet. That’s 1440 cubic feet (12 x 15 x 8). Let’s say your air purifier is rated at up to 165 cubic feet per minute (165 CFM) or 9,900 cubic feet in an hour. Dividing 9900 by 1440 reveals that your air purifier can produce 6.8 air changes per hour in this room.

That air purifier would be a great option for that room. Most experts agree that 6 ACHs are needed for those with severe breathing problems. At least 4 ACHs are recommended for typical allergy relief. In any case, never less than 2 ACH for any benefit and only with the most efficient air purifier.

Which brings us to the subject of efficiency. You cannot clean all the air that passes through an air purifier. Some may bypass the filter or the machine simply cannot remove 100% of the particles that pass through it.

The lower the overall efficiency of the system, the more times the air must pass through the air purifier to achieve the same cleaning result as a higher efficiency unit. This is why I recommend using only air filters with proven high system efficiency. It does the job effectively with less ACH and therefore lower fan speeds and less noise.

Putting it all together

So how long does an air purifier take to clean a room? Initially and with good ACH from 4 to 6, about an hour or so to reach a point that produces good allergy relief. Of course, give your body more time to shed its load of allergens. Just remember that the job of cleaning the air never really ends. You should run your air purifier continuously to keep the air as healthy as possible.

I also recommend that you use the most effective and efficient air purifiers you can. Two excellent resources that rigorously test and prove the value of any air filter they offer are achoo! Allergy.com and AllergyBuyersClub.com. Both sites also offer good educational information on air cleaning and allergy management.