Myth-busting

This morning I came across a website (more of an online store, actually) that claims that whole home air purifiers don't work. More specifically, the site talks about the inability of ultraviolet air purifiers to treat all of the air in a home. Well, we (L2B Environmental Systems Inc.) make ultraviolet whole home air purifiers, and I can assure you that they not only work; they work really well.

Here's what the website says:

Myth 4: Whole house ultraviolet light systems for central air conditioning units - These ultraviolet light systems are installed into air conditioning systems to kill mold and bacteria. They do not remove dust, particulates or airborne allergens from the A/C system, air ducts or from the indoor environment! These units are supposed to be installed so the ultraviolet lights are shining onto the evaporator coil on the air return intake side to prevent mold and bacteria growth on the evaporator coil and surrounding area, yet many of these units are installed improperly into areas of the air handler or air plenum where they can not do much good. Beware of UV light systems that produce ozone! Many of these UV light systems produce ozone at levels that cannot be controlled! Too much ozone can be an irritant to people with asthma and lung problems! I have experienced ozone producing UV light systems that created so much ozone it burned my eyes and throat. And I do not have asthma or any lung problems at all! Some of these units are also produced with non-ozone producing UV bulbs. However please note, if an air conditioning system is clean and installed properly and it has a high quality self charging electrostatic or pleated air filter in it to protect the air handler and evaporator coil from dust, the chance of the evaporator coil and the rest of the system becoming contaminated with dirt, mold and bacteria will be greatly reduced. We recommend properly cleaning your air conditioning system and duct work while installing an upgraded quality air filter instead of a ultraviolet light system. Please know that ultraviolet Light units for your air conditioning system are not whole house air cleaners even though people will claim that they will keep your entire home clean!

Now, in all fairness, some of what's said above is true.

The majority of ultraviolet air purifiers/UV modules sold online and in big-box stores usually consist of one or two low power (16-36 watt) UV-C lamps and a ballast (power supply). A product in this configuration is only suitable for evaporator/cooling coil irradiation, contrary to what the manufacturer may say about it being able to treat all of the air in your home. These kinds of products cannot adequately treat the air traveling through your HVAC system. The reason for this is because ultraviolet irradiation works on a very basic scientific principal:

UV Dose = UV Intensity x Time

This means that the longer a virus, bacteria, or mold spore (for example) is exposed to UV-C light, the higher the UV dose it receives. The higher the UV dose, the more likely it is that the pathogen will be killed.

Ultraviolet modules work really well for disinfecting the evaporator/cooling coils because both the module and the coils are stationary. Even though the module may have a low UV output, the UV-C light has lots of time to work, which results in a high UV dose. To put it simply: you only need a little bit of UV-C light if you have a lot of time. If the same module were to try to treat fast moving air in your HVAC system, however, it would fail miserably. This is because their isn't enough UV intensity to irradiate the pathogens in the air that are moving past the light at high speeds. Low intensity and a limited amount of time equals a low UV dose.

Our ALL•AIR™ DH and DS systems are able to treat all of the air traveling though your HVAC system thanks to our patented coating technology. This coating is highly reflective and uses nano-particles to intensify and evenly distribute the UV-C within the duct. In combination with the high output UV-C lamps that we use, this allows us to deliver a significant UV dose in a very small amount of time, enabling us to treat all of the air passing through the system. For more information about this technology, click here. And because we believe in a comprehensive approach to indoor air purification, we also have three stages of air filtration in our ALL•AIR™ DH model.

Finally, I'd like to briefly talk the issue of ozone generation from UV lamps (I will be talking about ozone in detail in an upcoming post). Only some ultraviolet lamps produce ozone. UV-A (tanning), B and C (germicidal) lamps do not produce ozone. Only full-spectrum UV lamps and UV-V lamps produce ozone. That being said, some manufacturers have their UV-C lamps specially made to produce ozone intentionally. Always ask the manufacturer about ozone generation from their products regardless of the type of air purifier you're purchasing. Ozone is a toxic, harmful gas that has no place in occupied indoor spaces. Never buy a product that produces ozone for your home. For the record, none of our ALL•AIR™ ultraviolet air purifiers produce ozone. Our lamps are certified to be ozone-free from the manufacturer.

That's it for today. If you have any questions or comments, leave them below. Thanks for reading!

By Michael McLean
L2B Environmental Systems Inc.