If you are suffering from severe allergies or asthma, it is likely that you have found dozens of ways to avoid contact with allergens. Many of these tips, such as switching to anti-dust mite bedding, or removing sneakers before entering the house to avoid pollen, are great for improving indoor air quality.

Another procedure that has recently been suggested to improve indoor air quality is air duct cleaning. Can duct cleaning alleviate allergic diseases? Because there is still very little known about the positive or negative effects of this sort of maintenance, it is questionable as to whether or not it can improve allergies.

Most of the time, the dust adheres to the inside of the duct and is not redistributed into the house. Yet there is the exception– every house is different, has different kinds and amounts of air pollutants and would therefore have a different recommendation whether to clean the ducts or not. Typically, indoor activities like cleaning, cooking, smoking or simply moving around will give you greater exposure to contaminants than living with dirty duct work.

Q.  When is it time to try having your ductwork professionally cleaned?

 A.  If you have already neutralized other possible allergy-triggers in the house, but still have symptoms, then you may want to try having your HVAC duct work professionally cleaned.

If you have allergic tendencies towards molds, dust mites or animal dander, this may bring you much needed relief. Just keep in mind that the condition of duct work in every house is different and there is no guarantee that duct cleaning will drastically improve allergy symptoms like some companies claim. On the other hand, you may be surprised at the positive results!

Here are a few of the earmarks of dirty duct work:

1. Substantial, visible mold growth inside the ducts—this may be seen on the sheet metal of ducts or other components of your heating and cooling system.
2. Ducts are infested with vermin, such as insects or rodents.
3. Ducts are clogged with excessive amounts of dust and debris, causing particles to be released into the home from supply registers.

A few considerations before paying for a cleaning:

• If you see extra dust around or on return registers, this is not necessarily a reason to get your air ducts cleaned. It is natural for dust-laden air to deposit debris around the return vent as it is pulled through. Dirty vents can be removed and cleaned– and are not really an indicator of dirty duct work.
• Because most of your heating and cooling system is not accessible for inspection, if a specialist or service provider tells you that there is mold growing within the duct work, ask to see it for yourself. It’s easy enough to say that the mold is there even if it isn’t.
• Sometimes what appears to be mold isn’t actually a fungi. It will require an expert or lab analysis to determine that substance actually is mold. For about $50 some microbiology laboratories can tell you whether the specimen you sent them is mold or not. Insulated air ducts where the insulation has gotten wet and moldy cannot be effectively cleaned and will need to be replaced.
• The cost of having your ducts cleaned can be somewhere around $500 to $1000 dollars for each cleaning—this range depends on size, condition and other factors. Depending on the condition of your home and duct work, your duct cleaning service provider will let you know how often your ducts need cleaning.
• Biocide sprays to deter mold growth or spray-on sealants and encapsulants are often offered as part of a air duct cleaning, but be careful, because there is inadequate research to determine the effects that "duct treatments" have on people. The sprays could be harmless, or hazardous– not enough is known about them to be certain. As always, be extremely cautious with chemical treatments if you live with someone who has a lung condition.
• Improper cleaning can actually cause more indoor air contamination than leaving air ducts filthy. If the vacuum used to remove dust from duct work doesn’t have strong enough suction, the end result will be worse than before the cleaning. Stirred up dust, spores and dander will be spread throughout the house every time the system is running.
• As I mentioned earlier, there really is no proof that cleaning duct work will prevent help problems like allergies, asthma or other lung conditions. Likewise there is nothing published that would say it would be harmful to individuals with these conditions either. Ask the advice of a duct cleaning professional– just make sure that you find a specialist that is trustworthy.

Another easy solution to keeping ducts clean is installing a set of air cleaners made specifically for use with your HVAC. A UV in-duct air purifier eliminates spores so that mold can no longer procreate inside the HVAC system. Using a HEPA quality furnace filter in place of your ordinary HVAC filter will keep dust from entering ducts and being spread throughout the house. If you think that your ducts may need cleaning, ask a professional for advice.

Call the company that provides service for your heating and cooling system and see if they offer duct cleaning or could suggest a reputable company. For more information, check out the EPA's page on air duct cleaning. Already had your air ducts cleaned? Please post a comment with your thoughts on this topic!