!#8# How Long Does an Air Purifier Need to Clean a Room?

!±8± How Long Does an Air Purifier Need to Clean a Room?

Have you heard it said, "A woman's work is never done?" Your air purifier is never done either. There are six basic reasons why you need to clean your air continuously. Understanding each will help you get the clean air results you want.

Once in a While is Never Enough

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

The reason is simple. Indoor air is in a constant state of change. Particles, gases and microorganisms are constantly introduced by such things as foot traffic, coughing and sneezing, normal shedding of skin (dander) by humans as well as pets, your central heating and air system and other activities.

Six Facts About Getting Healthy Air

Most likely you want specific health benefits like allergy or asthma relief. What do you need to know to make certain your air purifier delivers those health benefits? Consider the following six issues:
Your personal sensitivity Dilution of pollutants Dispersion of pollutants 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 "tipping point." Personal health and environmental factors make this a moving target. Certain allergens may provoke a reaction today but not tomorrow. It depends upon your total load of irritants and physical stresses.

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

Why do I talk about dilution of contaminants and not total elimination? Because particles and gases do not stand still for an air purifier to capture them one by one. Normal particle motion disperses them equally throughout your room air.

This means clean air exiting your air purifier is almost immediately recontaminated by the untreated air. You can't hold clean air on one side of the room while cleaning the air on the other side.
This is why your air purifier should run continuously. Constant treatment reduces pollutants and keeps them at a low level.

Countering air cleaning is the reintroduction of new pollutants. Reintroduction is like a leak in a boat. In time the boat sinks. Your air quality will sink also if you don't stay ahead of the reintroduction rate for new pollutants.

Just as the boat needs steady bailing to stay afloat your room air needs continuous cleaning to stay healthy.
This is where ACH, or air changes per hour, comes into play. ACH indicates how fast you can bail your room air of contaminants.

ACH is determined by dividing the cubic feet of cleaned air your air purifier can deliver in one hour by the cubic feet of the room. Say your room is 12 x 15 with an eight foot ceiling. That's 1440 cubic feet (12 x 15 x 8). Say your air purifier is rated to deliver as much as 165 cubic feet per minute (165 CFM) or 9900 cubic feet over an hour. Dividing 9900 by 1440 reveals your air purifier can deliver 6.8 air changes per hour in this room.

That air purifier would be an excellent choice for that room. Most experts agree that 6 ACH is needed for those with severe respiratory problems. At least 4 ACH is recommended for typical allergy relief. In any case, never less than 2 ACH for any benefit at all and then only with the most efficient air purifier.

Which brings us to the issue of efficiency. Not all the air passing through an air purifier may be cleaned. Some may bypass the filter or the machine simply can't remove 100% of the particles passing through.

The lower the total system efficiency the more times the air needs to pass through the air purifier to achieve the same cleaning result as a higher efficiency unit. This is why I recommend using only air cleaners with proven high system efficiency. It does the job effectively with fewer ACH and thus lower fan speeds and less noise.

Putting It All Together

So, how long does an air purifier need to clean a room? Initially and with a good ACH of 4 to 6, about an hour or so to reach a point yielding good allergy relief. Of course, give your body more time to relieve itself of its allergen load. Just remember that you never really finish the job of air cleaning. You should run your air purifier continuously to maintain the healthiest possible air.

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