foul exhaust gas like smell in house
We moved into a new construction home late September 2011 in SW Chicago. In early October 2011, we started to smell a gas like smell in a 2nd floor bedroom located in the vicinity above the 2 furnaces, 2 air conditioners, water heater and 3 external exhaust lines. Our roof vent lines and radon line are also on the same (east) side of house. This smell is also evident at the top of our basement stairs. The gas company came out twice and said no natural gas leak. The smell disappeared entirely in the first week of November (when cold weather stayed). The first week of March (4 months later) the foul gas like odor reappeared after strong winds and warmer temperatures. We installed a 6″ fresh air return line from the bottom of the first floor down next to the furnace area in the basement thinking the house was too tight. This did not fix it. Thinking it may be a plumbing vent line problem, one week later we did a peppermint test on the plumbing lines. We detected faint peppermint smells in a few areas right away and stronger peppermint smells in the basement only the following morning but can't capture where the smell originates from. The smell is definitely the strongest in the 2nd floor bedroom above the combustion units and the basement combustion area and top of the basement stairs. We did check all the traps, toilets, ejector pit, etc. too with no success in finding the cause of the smell. I also turned off my hot water heater only for overnight because the smell coming out my exhaust pipes smells like the odor we get. But after doing this test, the smell still was there. There is no foul smell whenever the air conditioner is on or during the cold months between November 1 and March 1. Rain also dissipates the smell.
The smell almost always occurs when we open a window in the house and the temperature is above 65 degrees with no rain. If we open the 2nd floor bedroom window above the exhaust vents the odor in this room is extremely powerful as well as the smell in the basement by the combustion area and top of the basement stairs only. If we open other windows in other parts of the house we smell a faint smell in the first and second floor but still get a strong smell in basement by combustion area and top of the stairs. Again, this smell only occurs when the weather is above about 65 degrees and sunny.
The builder blames the smell on a water based concrete floor sealant and the moisture he says it created in the basement. We disagree along with other people/professionals who have been over to assess this situation. In fact, what we have found on the internet shows that a floor sealant is a good thing to keep moisture away. And the smell is isolated and not all encompassing throughout the house or basement! Our basement smells completely normal when the windows are closed and we have no moisture (no white chalkiness) under the water based sealant in the floor. I have been running a dehumidifier in the basement for the past month and the relative humidity is steady at 40% which is typical of a normal basement. Also as an fyi, I have carbon monoxide detectors throughout the house.
I am only guessing I have a back draft problem and need to know how to fix it.
Have someone come out and perform a worst case depressurization test of your combustion appliance zone (CAZ). You say the smell gets worse if you open a window directly above the flue vents? I must be mis-understanding you here, 'cause I can't understand what is surprising about smelling flue gas comming in through an open window directly above a flue pipe. Are we talking about a sidewall vent on a condensing furnace that is located under your window? If so, mystery solved.
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A blower door test will determine how much the house leaks.
Another test, a "worst case" draft test will involve turning on all exhausts in the house - bath fans and kitchen fans, and then firing the furnaces and water heater and testing the draft in them.
Regarding your furnaces - are they 80% efficiency which vent with metal pipe or 9% efficiency which vent with PVC pipe? If 90% do they have one or 2 pipes per furnace? Also for PVC vents, the installation instructions will specify clearances to doors and windows to prevent infiltration of the exhaust fumes.
Also inspect the air returns to ensure they are not loosely fitted and pulling in odors.
Thank you for the quick replies. It was 73 degrees and sunny this afternoon and we kept all windows in house closed for a test and the exhaust smell stayed at the top of the basement stairs only. When it is less than 65 degrees outside there is no smell whatsoever. Since the windows were closed there was no smell anywhere else in the house.
First floor never smells in the room next to the 3 outside exhaust vents. 2nd floor window is not directly above the 3 exhausts but rather on the near corner (exhausts are on SE corner; window is just on south at the same corner).
My 2 furnaces are each 92.1 efficiency with 1 pipe each furnace. Not sure about the PC vents installation instructions.
I am really hoping the CAZ worst case depressurization test or blower door test will find the problem! if a problem is found from one of these tests, what the normal resolution?
On a side note but probably related, whenever there is a cooking smell or say my wife is using nail polish remover, the smell lingers at the top of the basement stairs for quite a while too. Possible relation?
If it was 73* I expect the furnaces were not running. In that case the water heater is the most likely cause.
Originally Posted by rski8
The relationship to the outdoor temperature may indicate a weak draft that is insufficient when it is warmer outside, but that's just a guess from the scanty information.
Re. "normal resolution" of problems, that will depend entirely on the problem.
Re. smells lingering at the top of the basement stairs, I think it unlikely that your wife is removing nail polish in the basement. It may be that the top of the basement stairs and the vicinity just does not have much air circulation. Try running the furnace fans for a day or two as an experiment. If the odors do not linger there any longer then you should consider leaving a fan running, especially if you have a variable speed blower that can operate at a low circulation rate. That type does feel drafty.
2 other things I forgot to mention in my most recent post. My water heater is self ventilating (same type of unit as thread (http://hvac-talk.com/vbb/showthread.php?t=1003531)) Secondly, my 1st floor toilet runs on its own about every hour for 10 seconds (makes a hissing sound).. What is this? Too much pressure? Possibly related to the high efficency?
If you want a skilled combustion analyst go to; www.stopcarbonmonoxide.com and do a dealer search. They can do full combustion testing to find any exhaust spillage under any conditions.
Also make sure they do a leak sniff on all gas lines.
As for the toilet, the flapper inside is likely leaking, causing a need for the water tank to replenish. A new flapper is in order. (or whatever it's called)
Worry is a really gross misuse of one's imagination. -- PHM
No source found yet. Smell still exists. I am waiting for an air quality test to be done in the next few weeks to see if we can pinpoint source this way. Please explain your situation in more detail and maybe we can find some common ground.
I will post any info I gather once I have the air quality test/combustion test done. Do you have a specific room in the house that smells the strongest other than the basement stairs? If yes, where is this room in relation to the combustion units (furnace, water heater, ac)? Also just curious, did you paint the basement walls and/or seal the concrete floor in the basement?
Foul exhaust smell sounds more like sewer gas, especially when combined with peppermint test that did show up in air. Don't dismiss this. A good C.O. meter will detect even low levels of combustion products, and should be able to confirm or deny if smell is from water heater, appliances, etc.
IN THE MEANTIME.... get set up with a low level CO alarm!!!!
I'd focus on the sewer venting and pipes. This is a common place for builders to cut corners and get a low bid plumber in there, that's not a good skilled master plumber. Plumbing companies that do new cosntruction often use a lot of apprentices fo the work and not everything gets inspected. Could be as simple as a vent pipe comming loose, improper drain slope, no vent on a trap.
The purpose of a peppermint test is to determine if the plumbing drains/vents are leaking. If you get ANY PEPPERMINT odor, there are leaks. I don't know how they test for leaks in your area but in our area, new construction plumbing is tested by plugging the main sewer pipe, plugging or capping all drains and vents except for the highest vent in the house and then filling the entire system with water until water overflows the highest vent. Allowed to stay full for several hours, any leaks and/or non-welded joints will reveal themselves in short order. You stated that you immediately smelled peppermint when that test was done and that puts the building in the liability department. He had the house built and plumbing drain leaks are not allowed. Period, end of story. You need to have a conversation with that chap and let him know that the house doesn't meet minimum plumbing standards. If he/she resists, you may need to contact your local health authority and be prepared to move out until the problem is resolved. I strongly suspect, as others have already stated, that your odor issue is plumbing related, not combustion related. This is a serious health issue and potentially a life threatening issue (sewer gasses are explosive). You need to take definitive action and the sooner the better.
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