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Cleaner air for you
does kill microbes, mold, bacteria, and viruses, but there are some large caveats to that. “There are several factors involved in how UV light works: the light has to be of sufficient intensity within a specific distance at a proper angle for a sufficient dwell time. It can take an extremely long period of time to kill microbial growth. It may take 8 seconds to kill some bacteria, 80 seconds to kill some mold, or 8,000 seconds to kill some of the really hard-to-kill molds. If you’re trying to kill something on a stationary surface, you can do it with UV light unless it becomes shielded from the light. By the way, cumulative exposure has not ever been shown to work with UV light because, if a cell or the DNA in a microbial growth gets damaged while passing in front of a UV light, that doesn’t kill it — it will repair itself long before it ever passes through that light again. So you can’t put a UV light in an AC system and rotate the air through it and say that everything will eventually get enough exposure to be killed, that is not going to happen. “UV light intensity is cut in half by about every six inches that you move [away from the surface] so they have to be very close. You can’t get a lot of distance out of a UV light. UV light can be effective in killing microbial growth on a stationary surface. It can’t kill microbial growth in the air stream. “There are times when UV light can be beneficial in a home that has a properly installed and maintained air conditioning system. UV light eats up rubber and plastic and silicone and things like that. If you have a very wet installation and it’s difficult to control, and because of that you get microbial growth on the coils of your air conditioning system, UV light might be appropriate. That might be one of the ways to keep microbial growth off the coils. But if you have that situation, then you have a problem that needs to be corrected. You don’t need UV light, you need to fix the system because something is not working properly.” He notes that UV light is very harmful to the eyes and can cause severe burning of the retina, so it’s advised that you turn the light off before opening a door or cabinet where it is located. HEPA: “With the HEPA air purifier, you’re capturing particulate matter in a filter. Whether it’s bacteria, viruses, mold, or whatever, it’s trapped, it’s going to die, and it’s not going to leave that filter. HEPA air purification is the only clinically proven method of cleaning the air. If you go, for example, to a hospital where they require clean air in an operating room, or an electronics company where they have a cleanroom, they use HEPA or ULPA [a higher-grade filter; ultra-low penetrating air]. Without exception, that is what they use. We service cleanrooms and hospitals and deal with lots of these filters. “In hospitals, they might use UV lights for instrument sterilization or things like that, but they are not using it to purify the air, they’re not using Ionic Breezes or any of these things. They’re using either HEPA or ULPA because that’s the only thing that works. “A good HEPA air purifier will typically have some type of mechanism that pulls odors and gasses out of the air. They usually contain activated charcoal, embedded activated charcoal, or some kind of blend of potassium permanganate and charcoal or zeelites and charcoal. “Now just because something says HEPA on it doesn’t mean that you are getting HEPA performance. It depends on how the machine is designed, how the filter is put together, how the machine is sealed ... there are a number of factors. But a properly designed HEPA machine reduces particle counts in rooms by 90-95%. An average home might have a particle count of 1.5 million particles per cubic foot of air. You can’t see these things because most of the particles are too small.” Brown notes that HEPA is a government designation which was developed during the early days of atomic research and was designed to ensure that radioactive isotopes were pulled out of the air. Brown says that HEPA will capture more than 99.97% of all particles larger than 0.3 microns (a strand of hair is about 10 microns thick). “HEPA has become standard in air purification because it pulls out most of the substances that bother us,” he says. “Allergens and most bacteria are larger than .3 microns.” He also adds that since carbon breaks down ozone quickly, HEPA air purifiers are a must on ozone action days. Electronic and electrostatic air purifiers: [Note: Electronic air purifiers and electrostatic air purifiers are not the same.] “Most of the time with electrostatic systems, we are talking about a passive process where air flow passing over a substance creates a charge and those charges attract particles,” explains Brown. “If you put a good electrostatic filter with a low level of resistance in your home air conditioning system, it can greatly improve your particle capture rate. But an electronic |
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