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Question DetailsAsked on 8/2/2016

Should I get my air ducts cleaned before having an in duct air purifying system installed?

I'm an asthmatic. It was suggested that I get an APCO or GPS UV air purifier system installed in my ducts. I was told that it would eliminate mold mildew dust mites and allergens that may be contributing to my breathing problems. Is this a good idea???

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Generally, the lint in the ducts does not break free unless the ducts are being worked on or in a significant shaking, like a major earhtquake or near-miss by a tornado or hurricane which shoots high-volocity air through them. However, if mold and mites and such are your problem, then they would likely be on teh dust in the ducts if there is a buildup, so I would consider it - along with a mildewcide treatment after the cleaning. More likely to be helpful in a huimid climate, where mold growth in the ducts is more likely, than in a dry climate.

Certainly, a primary thought should be making sure you have a high-efficiency (HEPA) air filtration system - being sure the airflow is suitable for your unit. In rare cases that means putting a larger air intake throat with filter slot on the unit to handle a larger size filter - a couple hundred $ job usually. Also, the air filter slot should be sealed when in use, not just wide-open slip-in slot. There are "doors" that can be put on to do this, or just duct tape the openign after filter installation each time.

On the air purifier system - the GPS system website reads an awful lot like the warning sheets from CPSC on consumer scams about non-ozone ion air purification systems - and the "cold Plasma" - well, sounds like bunk to me. Plus, with the way it is described, would have to be put inline BEFORE the air filter to actually remove anything, which most systems are not set up to do, and would do nothing about mold growing on the evaporator coil, if you have central A/C.

Ultraviolet light system - though usually takes 2 or more bulbs exposing each face of an A/C evaporator (so typically 4 or 6 bulbs depending on whether flat plate or A-coil shape) to actually effectviely kill the mildew/mold growing on the evaporator coil. At normal airflow in ducts, to get enough exposure time to actually kill anything in the airflow I don't remember the normal number for residential - but something like about 8-10 feet of run exposed to the normal bulbs to have a killing effect, not the few inches typical in a residential system. Hospital UV systems work well but typically run in the several thousand $ and have a bank of lights all aroudn the perimeter of the duct to fully expose everything passing by - and have a HEPA filter downflow of them.

If your A/C evaporator tends to build mold, then a UV light system to kill that might be of valule to you - but unless you go for big bucks the ones the air just flows past are pretty ineffective.

I would ask your allergist for advice, especially at to whether it is particulates or mites or mold or what that is affecting you, because some you can filter out, some you need a biocide system to kill if that is what you need.

There are also air vent filters - HEPA filters which go in the room registers and are changed every few months (so quite a bit more hassle than just the main filter) but can remove a lot of material, and most importantly are downflow of the evaporator coil and the ducting so they filter the air just before it comes into the room. However, you should not install these (plus vent/register sealing is needed to make them so all the air has to pass through, not around, them - and the system needs to be checked to be sure that the airflow is not being restricted too much. Sometimes it is necessary to install a stronger blower to compensate for the added airflow friction through the filters.

Another thing to consider - commonly the most troubling source is carpets - both trapping and then rereleasing dirt/dust/allergens brought into the house, and also carpet and dust mites and shedding of fibers from the carpet. Frequent wet cleaning or total replacement with hard flooring has been known to significantly reduce the problem for some people with respiratory issues.

Another thing to discuss with your allergist - some asthmatics are most affected when and immediately after sleeping, when low air circulation in the lungs allows buildup or more contaminants in the lungs and promotes asthmatic responses - so it may be a portable room air filtration unit near the bed would be more effective for you.

A lot of people try all sorts of solutions - but going to hard floors, having good HEPA filtration filtering both the incoming makeup air for the HVAC system and the return airflow (which is normal but not universal in forced air (ducted) systems), and frequent dusting and vacuuming is commonly the most effective for this sort of condition - though in severe cases serious multiple filters (sometimes including one downflow of the evaporator coil or the register filters) or an electrostatic precipitator downflow of the evaporator is necessary.

For professional advice, beyond that of the allergist (and he might be able to recommend one to you) a certified Indoor Air Quality specialist is what you would be looking for.

BTW - if any such work is being done for health reasons under doctor's orders/ prescription, check on tax deductibility of its cost - though when you sell the house you may be taxed on the recovery of that deducted cost.

Answered 4 years ago by LCD

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