Thousands and thousands of room air cleaners are bought each year, and most of them won’t do the job the unsuspecting consumer thinks it will do.
We’ll get to that in a minute, but before we do that, let’s talk about the three types that are most often sold.
The first, and most common today is the HEPA or HEPA style air cleaner. These devices use a HEPA certified filter which by definition is 99.97% efficient on particle sizes .3 microns and above. That’s pretty efficient and will do the job removing most common household dusts, if they’re captured.
The second type, ion generators, uses ionization to “capture” the dust and draw it to the floor or other surfaces.
Lastly, we have the electrostatic precipitator which also uses ionization but captures the dust on a collection cell incorporated into the air cleaner.
Let’s discuss the features, benefits and issues with each.
The HEPA or HEPA style generally has the most efficient filtering system available. The filter, if sealed properly will capture a very high percentage of dust and other particles, which is what you want. When it gets full however, the airflow becomes restricted limiting the amount of dust that is captured. When the airflow becomes too low, the filter needs to be replaced. Replacement HEPA filters can run anywhere from $50 to $300 on up, depending on size. That can be serious sticker shock for most homeowners. If you buy one of these machines, make sure you know what the replacement cost and the frequency of replacement and weigh that into your decision. One of the questions usually asked is “how long will the filter last”? Unfortunately, no one knows how dirty your house is so they can usually only give estimated life. For the sake of overall cost of use, I’d estimate the cheap ones get replaced twice a year, the expensive ones will generally last up to 5 years, which may be a better overall value.
The ionizer has been a very controversial product over that last 10 years. Do you all remember the Ionic Breeze? Sharper Image sold this device and apparently made unsubstantiated claims to its efficacy which ultimately may have led to the demise of the company.
They’re not the only ones. Other manufacturers have been slapped with Federal and individual lawsuits because of their claims. The other problem with some of these devices is that they give off too much ozone, which can be harmful to humans.
Ozone can be reduced with carbon after filters but many of the ionizers don’t have those installed. And the carbon must be replaced periodically depending on use and other environmental factors.
I’d be very careful before buying an ionizer. Make sure to read everything you can about them first.
Electrostatic precipitators are also very popular for home use. They start out very efficient and if maintained properly will maintain that efficiency. Most manufacturers employ what’s called a unicell which means the ionizing section and the collector section of the filter are all in one. That makes it easy for cleaning, which is usually accomplished with a non-alkaline detergent and hot water. These are the same filters used in a variety of electronic whole house air cleaners, which many people are familiar with. The only real downside of the ESP is the maintenance, which does need to be done to be effective. If you’re not interested in cleaning filters, this may be a factor for you to consider. ESP’s can create a small amount of ozone, but usually it’s well below the threshold considered safe and many machines come equipped with carbon after filters which can reduce or remove ozone emissions into the room.
With all of these air cleaners, room sizing is important. In general, most of these are most effective when in a room where you get 8-12 air changes an hour. A simple formula for determining how large an air cleaner you need is CFM = (L x W x H x Air Changes per Hour) / 60 min. Where LxWxH are the room dimensions in feet.
Here’s a link to a sizing calculator to help you determine how large a room air cleaner you need.
Regardless of what you may decide to buy, make sure to do your homework before you do.