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Question DetailsAsked on 7/21/2017

Occasionally my inside air quality gets a stuffy, dry smell that burns eyes & throat..AC freon leak?

Smell happens any time of year but is evident only periodically and can detect it in most rooms when present. Started abt 2+ yrs ago. Freon was quite low in central AC and was just refilled but leak not looked for...same story, told I might need to replace unit. Could freon leak in basement be the culprit? Or could this just be dust build up in vents etc? It can be evident when furnace or ac hasn't even been on. It has me baffled. Any suggestions on where would be best for me to call to have this figured out?

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Can't quite diagnose from probably thousands of miles away - but here are links to some related questions with answers (and one has links to a LOT of related questions with checklists of possible causes and hints on diagnosing the source), and some reference articles on the subject of indoor air quality issues:

In a residence, known causes include the following list (in no particular order except 0) comes first and is also probably the most dangerous aside from maybe #4). And of course in your case this would have to be a source which stays in effect or could continue for 2+ years and is a potential source during the times you have noticed it i.e. appliance likely would only cause it when operating) - and some sniffing around at potential sources may readily eliminate some of them using the following as a checklist:

0) fuel-fired (as opposed to electric) heating unit (furnace. boiler, water heater, fireplace, wood stove, space heater, etc) exhaust flue disconnection or leakage resulting in exhaust gases getting into the house.

1) leaking A/C refrigerant - though to continue off and on for 2+ years and year-around would presumably have to be leaking an awful lot, and generally only leaks signfiicantly (for long periods if a small leak) when unit is being used, so if you have winter in your area I would say that is less likely source with it occurring year-around. (Large leaks, which would be more likely to cause a reaction, would not last a year or two without the unit running out of gas). Normal small leak is so dilute, if leaking off maybe 5-10 pounds of refrigerant over the ncourse of many months, that you would not be expected to have noticeable effects. Resident complaints due to refrigerant leak (excluding ammonia leaks, geneally not used in homes) tend to be only with large leaks, venting pretty much the entire charge in days rather than months. Almost all health effects from refrigerants are reported as being from occupational, by HVAC or assembly plant workers.

Of course, refilling the unit without fixing the leak is not only illegal but also does you no favor because you will just be paying (commonly around $500 and sometimes twice that) to refill it again soon down the road. But fix the leak (or replace unit as applicable) and you also eliminate one potential source. [You can find a lot of previous questions with answers and thoughts on the repair/replace decision in the Home > HVAC link under Browse Projects, at lower left.]

2) leaking solvents, paints, cleaners etc - check for leaking containers under kitchen sink, laundry area, garage or workshop, dead storage in basement, etc - though to continue 2 years would presumably have to be a large container leaking slowly

3) auto exhaust leak into house - obviously occurring soon after driving car in or out of garage, or from idling vehicle outside or in neighbor's yard

4) leaking fuel from cars in garage - though you should also be smelling fuel smell in that case, at least in the garage when it has been closed up for awhile. Ditto to leaking antifreeze or other auto fluid.

5) "Dirty sock syndrome" - from mold/mildew buildup on A/C evaporator coil - though again once the A/C season ends, that dries out and goes away pretty quickly (in days) in almost all cases unless the A/C coil is incredibly dirty - and would be MUCH stronger when blower is moving air through the ducts, at least at the start of the cycle

6) exhaust gases (auto or furnace, barbecue or smoker, burn barrel, etc) from a neighbor's unit or property. Obviously if from a neighbor's separate house you would normally expect to smell fumes outside too unless their furnace exhaust vents close to an air intake point at your house. Most common with condos and apartments and townhouses and such - multi-unit dwellings. Can also occur from back-drafting due to exhaust flue issues - blockage, change of units so the flue is no longer properly configured for the units in use, etc.

7) significant mold/fungal growth in attic, basement or crawlspace, or in framing due to a water/sewage leak - but almost always will be associated with a strong mildew, mold, or organic "toadstool" or "punk wood" odor as well

8) like above would normally be expected to be associated with a strongish obnoxious odor - stagnant water in basement/crawlspace or sump pump pit

9) overheating/burning plastic in furnace or blower unit or control board - sometimes can go on for many months before it finally fries itself. Ditto to an excessively dusty fan motor (furnace, A/C air handler, attic or whole-house or kitchen or bathroom fan) burning off dust when it runs. Course, if it occurs without these units operating that pretty much rules them out EXCEPT for case 6) - exhaust leakage if there is a standing pilot. Turning unit totally off (including pilot light) for as many days as it takes to rule that source out might eliminate that potential source.

10) wet creosote in chimney - causes acids which can create a strong caustic odor and burning sensation - usually strongest after rains and on very humid days (especially rainy days). Aggravated of course if cap on top of chimney has rusted through or been blown off so rain water is getting in there.

11) allergies - though if affecting more than one person in a house where it did not cause issues before, less likely. Can be caused by signficant dust buildup in ducts, though many ducts which have a heavy coating of dust cause no problems as long as the humidity in the air through them is low enough (below about 55%) to not grow mold in the ducts.

12) overheating heated drying or steam unit on washer or dishwasher, or burning lint in dryer/dryer vent which needs cleaning - obviously only when or soon after they have been in use

13) a very common source, though should have been much stronger right after installation then tapering off with time, is chemicals from new carpet, paint, flooring, countertop, occasionally new cabinets or other furniture, etc

14) leaking sewer gas due to cracked pipe or plugged vent stack, or much more commonly, leaking out from an unused drain or floor drain because the water in the trap has evaporated, so the gases can now come into the house. This can also happen when a sewer pipe is partly blocked, so when large flows of water go down the pipe (usually Washing Machine or full tub emptying is first occurrence) as it fills the pipe it can sometimes push sewer gas (which may smell like sewage or like Sulfur Dioxide gas) past the water in a trap and into the house. Rarely from septic tank/leach field, and that odor would be described as damp, sewage smell - not stuffy dry

15) kid doing/using something in their room, garage, adjacent shed, etc - craft or hobby chemicals or glues, chemistry set, paints, etc. Corollary - neighbor operating his crack house or meth lab - though of course if when you notice it going outside should make the smell much stronger and also allow you to figure which direction is it coming from (assuming you have a slight breeze at the time).

16) fuel oil tank leaking - though should be thick, oily smell in that case

17) old coal bin getting wet and causing coal tar gas to enter the airspace - sharp, tarry (similar to freshly tarred drive or roof), acidic fumes

18) rotting woodpile - inside house or close to it outside - but smell usually like in 7) above

19) rare - but large insect nests can sometimes cause this sort of effect with the pheromones or whatever they put out - a large carpenter ant or termite nest can cause a very strong burning sensation in nose and throat

20) critter nest in walls or attic - though usually smells like rotten food or urine

21) allergic reaction to some piece of clothing or furniture you bought a couple of years ago - but presumably would be much stronger reaction when in close proximity/wearing the clothing/sitting in/at the furniture

22) VERY rare in residential situation, but Halon or similar fire protection chemical leaking out of fire suppression system (a few people who do a lot of shop work have automatic discharge Halon fire extinguishers mounted over their paint/chemical locker in garage or shop).

Think what happened/changed 2+ years ago which could have introduced this contaminant - new appliance (HVAC or otherwise), new interior finish, new insulation, etc, particularly if it started off suddenly. [Duct /mold /rot related issues tend to develop over months-long periods]. Also if any outdoor source came into play at that time - new industry or commercial operation nearby like a refinery, chemical operation, dry cleaner, neighbor who does auto or shop work or outdoor smoking (tobacco or barbecue/fish smoker) at his property, etc.

Try walking around to eliminate possibilities - and since occurs in most rooms sounds like it might well be a source in or being picked up and carried through the house by the HVAC system, which might concentrate your initial search on the ducts and near the air handler/furnace. Pay particular attention to whether it is occurring right after operation of fthe furnace, A/C or water heater or such.

If you have a friend/neighbor who you are not embarrased to ask about this, if they happen to be in your house when you notice the issue ask them if they can identify the odor. Because this is intermittent, unless you can find some condition or event like an appliance running or basement door open or windy or very hot/cold day (which can pull air through the enclosed spaces in the house and thus pull the odor out into the rooms) which is connected with the issue, it is tough to call in a professional to evaluate it because odds are it will not happen while he is there.

Sometimes using masking tape and plastic sheeting to block off vents and door and letting a room sit with no ventilation, one room at a time, can help tie down the source.

If you are unable to track it down yourself, a Heating and A/C contractor to inspect your HVAC equipment and exhaust flues, including running a CO sniffer around, and to see if your ducts have moldy or very heavy dust buildup, might be a good next step. (Probably combining with a routine servicing might save a bit on $).

Failing that, an Indoor Air Quality company (no Angies List category for that) could do air sampling, but expensive (commonly several thousand $ unless they find something obvious right off the bat with an Oganic Vapor Analyzer) and for intermittent issues commonly fails to find the source.

Another source sometimes used before going the IAQ company route is a Home Inspector - to check out the entire house and basically eyeball for any potential cause, especially if you are not up to searching attic and crawlspace or unfinished basement, etc. They are used to looking for unusual things and crawling into/inspecting attics and crawlspaces and such, and some really get into this sort of "forensic" inspection work.

Push comes to shove (though probably $150-200 visit charge) - have doctor do blood test to see if your immune system is reacting to histamines indicating an allergic reaction - also a blood check for possible carbon monoxide buildup in the blood which would indicate an exhaust/flue leak into the house.

If you would, respond back using the yellow Answer This Question button right below your question, to tell us what the issue turns out to be - might help in answering similar questions in the future.

Answered 3 years ago by LCD

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