Headaches, sore throat, coughing, Asthma attacks, and difficulty breathing are a few of the symptoms that can be brought on by some air purifiers. Yes, that's right. Your air purifier may actually aggravate many of the health issues you hoped it would solve. Fortunately, all air purifiers do not cause these difficulties and some do work as advertised. But, how do you know the difference? Let's take a look at what makes some kinds of air purifiers work wonders for your health and well-being while others can be unsafe.
Before we consider the merits of air purifiers, let's look at the many varieties in the market today. The number of them can be mind numbing at times, and, each seems to make one claim after another. To help sort through it all, I've simplified the problem by categorizing them into groups based on the technology they use - noting that some air purifiers use multiple technologies in their design and cross these boundaries. Here are the general technologies used in air purification products.
Ozone generators - These types of air purifiers intentionally generate large amounts of ozone that is pushed throughout a room. Ozone is a purifying gas that kills living organisms such as mold, bacteria, and your pets in large enough quantities - more on this later.
Electronic air purifiers - These types of air purifiers draw in air, which becomes electronically charged.Air molecules then adhere themselves to dust and other particulates much like static electricity causes clothing to stick together. There are variations and characteristics of these types of products, which will be discussed later in this document, which include Electrostatic Precipitation, Ionization, UV light, and Corona Discharge.
Mechanical filtration - These types of air purifiers draw in air that is mechanically forced through filters that remove airborne particulates. There are a few types of these as well including HVAC filters, portable air purifiers, and ceiling mounted air purifiers.
Experts agree that ozone is harmful to your health. Certain regulatory bodies have taken action on this issue and air purifiers that generate ozone are actually banned in some places.[i] Certainly, these products generate significant amounts of ozone that, if inhaled, can cause long-term damage to olfactory cells and lungs[ii]. Even more concerning is that symptoms can disappear after repeated chronic exposure, making people unaware of the damage being done to their respiratory systems[iii]. But, even small amounts of ozone can be harmful.A Canadian study found that measurable bronchial reactivity can occur at ozone concentrations as low as .08 parts per million over a seven hour period[iv]. Even when not directly inhaled, ozone can be harmful.For example, ozone can react to common household cleaners such as terpenes, which are more commonly known in pine and citrus fragrances. In the presence of ozone, terpenes form formaldehyde, a Group 1 human carcinogen[v]. Ozone can even cause rubber and plastic to deteriorate prematurely in quantities as low as 0.35 parts per million[vi]. Imagine what it does to our bodies. Ozone, even in small amounts, should be avoided and air purifiers that generate it should not be used.
Air purifiers that generate ozone can clearly be unsafe, but, what about electronic air purifiers that claim to be ozone free? It may surprise you to know that electronic air purifiers also create ozone as a byproduct of their operation.In fact, in tests by the California Air Resources Board, all of the electronic air purifiers studied generated ozone[vii]. A Consumer Reports article agrees, stating that "all create some ozone" when referring to electrostatic precipitator air cleaners[viii]. This is really not that surprising when you consider the technical method by which electronic air cleaners operate. In general, these products draw in air that becomes statically charged by means of passing air molecules through an electrical field - essentially a spark. Have you ever smelled ozone from an electrical short in your home? Electrical air purifiers create a controlled version of this in order to operate. It is simply physically impossible for them to operate without creating some ozone, regardless of the manufacturer's claims to the contrary[ix]. In fact, the UV light and corona discharge technology often used in these products is also the technology used to create ozone in ozone generators[x]. Some units are available with technology claiming to eliminate residual ozone byproducts, however when these have been tested, some results have shown that ozone is still being generated[xi]. In addition, there is evidence that ozone generation may significantly increase if electronic air purifiers are not maintained properly in accordance with the manufacturer's instructions[xii]. Who has time to be sure every maintenance procedure is followed in accordance with the manufacturer's instructions? Our recommendation is that these products should be avoided.
An often-overlooked question is - What happens to the particles that have been charged by an electronic air purifier?Some particles can be captured on oppositely charged plates in electrostatic precipitators. If plates are dirty or if you have an ionization unit, a huge number of charged particles are blasted throughout the room - on the order of 1,000,000 to 10,000,000 per cubic centimeter[xiii]. So, what does happen to the ions?In the simplest terms, they combine with dust and other airborne particulates and adhere to the nearest surface such as a wall, ceiling, furniture, curtains, etc. In fact, they adhere to surfaces at such a significant rate that the industry refers to the dirt that settles as the "black wall effect." This dirt will eventually become neutrally charged and fall off the surfaces or get kicked back into the air[xiv]. Since ionization doesn't filter particulates out of the air nor kill mold and viruses, these viable particles continue to accumulate in the room. Some products use UV light and claim it kills the live particulates. Let's say you wanted to use UV to kill the influenza virus - actually, a fairly easy virus to kill. It would take 6,600 microwatt seconds to do that job[xv]. That means you'll need you'll need to expose the air for one second to a UV bulb rated at 6,600 microwatts. But, with air being pushed by a fan, how long will it be in front of the UV light.For example, if the air is in the presence of the light for one quarter of a second, you'll need a 26,400 microwatt UV bulb. Some bulbs are 50 microwatts while others are 18,000.UV light is a dubious solution for killing live particulates in free flowing air applications.In addition, UV lamps lose about 60% of their germ killing strength in the first year[xvi], so plan on changing the bulbs often to get any benefit at all.In any event, you'll still have to deal with dirt on surfaces in the room. Certainly, you can dust, mop, and clean fabrics in the room more often. But I wouldn't want to clean these concentrated particulates without a dust mask. And, who wants to buy an air cleaner just to end up cleaning more?
The safest most effective way to purify air is to filter it mechanically. And, the only way to effectively filter air is to move a lot of it. This creates a challenge for all but a few air purifiers. Objects in the room often block smaller portable units that sit on the floor or a shelf. Beds, chairs, desks, and other furniture make it difficult for air to freely flow to the units. If the airflow cannot reach every area of the room, you simply cannot get that air filtered. Even if proper airflow can be managed, most portable air purifiers don't have the air volume capacity necessary to filter enough of it. The industry uses a term called CADR or Clean Air Delivery Rate to express the volume capacity of an air purifier. While it is a bit more complicated than this, it roughly equates to the CFM or cubic feet per minute capability of an air purifier. The higher the CFM the more air can be moved through the filter. Some floor models have a CFM of less than 100, which is a very low volume of air. Even the CADR test itself can only test a max CADR of 450. Why only 450? The Association of Home Appliance Manufacturers (AHAM), which is funded by appliance manufacturers, has determined that a CADR of 450 is the highest score necessary to serve the needs of the appliance manufacturers in their organization. However, we do not believe that CADRs in this range are sufficient to perform adequately. To put that in perspective, at a CADR of 250, an air purifier only filters the air in a 400 square foot room about 4.6 times an hour - and that assumes the airflow actually reaches all of the air in a room. Even your home HVAC can beat that, filtering the air about 7.5 times per hour - less with a HEPA filter. But then again, if you put a HEPA filter in your HVAC system you may be asking for trouble as some units develop problems due to the increased pressure that results from pushing air through a more dense filter material[xvii]. Even if you could, filtering the air 7.5 times per hour is still not sufficient to remove dust, pollen, mold spores, pet dander, and other airborne particulates. To do an effective job of filtering you need to filter all of the air in a room 20 to 40 times per hour - that means a CFM of about 1,100 to 2,200. At this level of filtration, triggers for Asthma and allergies are significantly reduced - even highly infectious disease doesn't have a chance[xviii]. And isn't breathing cleaner healthier air and having the opportunity to improve your health and well being the whole point of an air purifier?
To safely and effectively purify the air, you need an air purifier that has the following characteristics:
Does not generate ozone
Is not an ionization or electrostatic precipitator
Provides for a proper airflow to reach all the air in a room
Mechanically filters the air
Has an air filtering capacity of 1,100 to 2,200 CFM
So, what's our choice? Without naming brands, we believe some ultra high capacity portable models can do the job, if you can stand the noise. We also like ceiling mounted models. They are out of the way and in the best location to promote proper airflow to reach every corner of a room. Some ceiling mounted models come with a motor, again, if you can handle the noise. Others mount on a ceiling fan motor. Those that mount on a ceiling fan motor are an interesting choice as they are nearly silent and have no motorized parts to break. I suppose a ceiling fan motor could break, but, when is the last time you had that happen? Those units are also highly energy efficient, using less electricity than a 100 watt light bulb.
You can expect to pay between $400 and $1,500 or more for an air purifier that will do the job for a room that's about 400 square feet. It may sound like a lot. But, I'll bet it's cheaper than your Asthma and allergy meds.Besides, how much is it worth to breathe easier, sleep better, and be healthier? Air purifiers can do a lot to improve your life, health, and well being - but only if they're effective and safe.
[i] www.cleanresources.net/statebans.pdf.pdf and www.calutech.com/ozone-air-purifier.htm