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Community and Q&A

Why is My Basement Making Me Sick?

SpeedRacer220 | Posted in General Questions on


I have been having trouble figuring out what is making me sick in the basement and wondering if any of you experts have any ideas I can try.  I have been hunting on and on without luck.

I moved into a bungalow house recently after a month or so of renovations.  It is a bungalow and there are big open stairs down to the basement which is about 1500 sq ft.

During renovations, I did not live in the house but came by and spent a fair amount of time here (sometimes helping out) without any issues in the basement.

Now, shortly after moving in, when I go down there (almost if there is some magic threshold that I cross when I get close to the bottom), I feel nauseous almost immediately and sometimes, I have headaches.  No respiratory issues.  I walk back up and I recover.

My wife, friends and family members have been down there without any complaints like mine.

Suspects considered:

Mould–A few of these tests were run and while there is some mould, I am told I should be experiencing respiratory issues too.  I have also been running various air purifiers, with HEPA filters, which all appear to show good air quality.
Radon–Checked and fine.  In any event, I don’t think radon causes these immediate reactions.
VOCs–Checked and low.
CO2–It can get up to the 1000-1500 range but I have been there down when it is at 500 with windows open for a while and still feel the effects.
Humidity–Generally in the 50%.
Pressure–Checked and normal.

In terms of the renovations, we put in new vinyl laminate floating floors ( with underpadding (!-2).

In a big space, we had wooden panels which our painter painted white.  Painting was the last thing for the renovation.  I know they used an extreme bond primer for the panels.

Anyone have any ideas for what else I can check?  Grateful for any advice.



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  1. Expert Member
    Zephyr7 | | #1

    I would check for carbon monoxide too. Any leaky flue pipes could be a problem. I experienced that myself once when I had a water heater backdrafting during some unusual wind and just the right combination of doors open at the time.

    You probably wouldn't recover right away if you were senstive to mold -- mold sensitivity usually lingers a while.

    Check that nothing is growing in any of your air filters or purifiers, and be careful with air purifiers -- especially any that use ozone. Ozone is a pollutant.


  2. Aaron_P2 | | #2

    Like Bill, my thought was you were missing carbon monoxide. I stayed in a rental house for a vacation and my mother complained of the same feelings. A couple nights later the carbon monoxide detectors went off at 3am - I think it was a bit colder that night and the furnace ran a bit more triggering the alarm. The standard detectors allow for quite a high level of carbon monoxide before alarming.

  3. SpeedRacer220 | | #3

    Thanks. Sorry - I left that one out but have checked it. I called the gas company and they (embarrassingly for me) sent the firefighters to check it out. They found nothing. I also have two carbon monoxide monitors downstairs.

    Would carbon monoxide only linger on the bottom floor or would I expect that to come upstairs?

    I do have a wood fireplace downstairs but the damper is closed. How would I go about checking if there are leaks?


  4. Jennifer M | | #4

    In addition to the good answers you have already received, I would consider an allergic reaction or sensitivity to something new in your basement. One way to test for an allergy is to have your wife bring up a small amount of each new item (piece of vinyl tile, a bit of paint on a piece of cardboard, etc) ONE AT A TIME. Sit with each new item in an area in your home that doesn't bother you (your kitchen, for example). If you can sit with the item close to your face for 10 minutes, no reaction, try the next item. It may be as simple as that.

  5. Expert Member
    Michael Maines | | #5

    What is the lighting source? Is it different than the lighting source on the main level? Are there windows to the exterior? Have you noticed any difference relating to the time of day? Is there flooring or other surfaces with patterns, or is everything solid color?

  6. SpeedRacer220 | | #6

    That is such a good idea Jennifer. We have been wondering whether it is the flooring and thought that the only way to test was to just rip ALL the flooring out (which would be devastating).

    On the fireplace, I had them "inspected" but not cleaned (stupid me). In that process, they did mess with the damper and it was previously blocked with cardboard and stuff. I'm going to see if the fireplace inspector will clean it. In the meantime, let me just block the opening.

  7. SpeedRacer220 | | #7

    This may be a stupid question but is carbon monoxide being produced even if there is no fire burning? It may very well be a malfunctioning damper and the negative pressure in the house drawing stuff in. Does this make sense at all? In a panic, I stuffed the fireplace opening with a whole bunch of anything I could find to see if that helps until the fireplace expert comes.

    1. Expert Member
      Zephyr7 | | #8

      Carbon monoxide (CO) is caused by incomplete combustion, so you have to have something burning before you get any carbon monoxide. In a typical home, the usual suspects for carbon monoxide are what are known as "naturally aspirated" gas appliances. The most common of these are furnaces and water heaters. If neither of those is running, you shouldn't have any new carbon monoxide forming -- but you may have a buildup of CO from the past runs. Note that natural gas fired water heaters that don't have blowers tend to be very, very quiet while running, so you might not even realize they are on. The easiest way to see if that type of water heater is running is to see if the flue feels warm. DON'T touch the flue -- it might be VERY hot -- just hold your hand near enough that you can feel for warmth. If the unit has been running for more than a minute or so, the flue will be noticeably warm.

      I'd be surprised if stuff is being drawin in from outside and bothering you, but I suppose that is possible.


      1. SpeedRacer220 | | #9

        Thanks. My heater is electric and my furnace has only been on for air conditioning. No heating yet. I would assume that is OK. Firefighters also did not find any CO issues with the furnace room.

        Wood fireplace has not been on for at least 2 months. Maybe it is the creosote but symptoms don't seem to track.

        I'll see if it helps and report back. Desperate to try everything.



        1. Expert Member
          Michael Maines | | #13

          If you're desperate, consider answering my questions that relate to lighting--some types are known to cause the issues you mention. I understand and agree that it's more likely an IAQ issue, but that doesn't rule out vision-related problems.

  8. Hammer 🔨 | | #10

    Also consider motion sickness from design features. What kind of floor design do you have? I know it sounds silly but if air has been tested and everything is normal consider a sensory problem in the room that could be lighting, design, etc. that would explain why you would spend hours during renovation and feel fine until space was finished.

    1. SpeedRacer220 | | #16

      I wonder how I could test for design. Should I blindfold (seriously) myself and go down there? My wife has suggested that.

  9. SpeedRacer220 | | #11

    Thanks Hammer.

    I have not really left the air issue yet.

    One odd thing I have noticed is that the skyrocketing of the CO2 and VOCs increase when I turn on the air conditioner. If the windows are closed, that is when it really goes up to the 1000-1300 ppm.

    Does this give anyone else other ideas? I wonder if something is wrong with my air conditioner and drawing in stuff - but does an air conditioner draw anything in from outside?


    1. Expert Member
      Zephyr7 | | #12

      Air conditioners don't make CO2, even if they are leaking refrigerant. VOCs are usually from stuff with solvents, so probably aren't a big concern unless you recently painted, cleaned something with a cleaner, used a lot of glue, etc. Bringing in outside air shouldn't INCREASE CO2 levels either, unless you are in a very unusual situation.

      My first thought is that you have something growing on the coils and/or filter of the air conditioner. I'd check that first. There are cleaners to use to clean the coils, and you can usually wash the air filter (some have to be replaced, just make sure you know what kind you have). See if that helps. Condensate, the water that condenses out of the air onto the cold air conditioner coils and runs out of the unit, tends to grow stuff, some of which can be pretty nasty. Disinfecting cleaners will help greatly if this is where the problem is.

      If you do have a refrigerant leak, it's easy to test for this if you can't smell it (not all refrigerants are easy to recognize by smell). Have a mechanical contractor come out (HVAC company), and ask them to "wand" the air conditioner to check for refrigerant leaks. The wand is like an electromechanical nose that sniffs for refrigerant. If you have a leak in a window mounted air conditioner, it needs to be replaced. If this is a central air conditioner, leaks can usually be repaired.

      In my experience, the most common places for refrigerant to leak are schrader valves (similar to what is used to put air in tires), flare fittings (fittings with a nut that tighten with wrenches), brazed connections subject to vibration -- especially TXV assemblies, in that order. The same mechanical contractor who checks for leaks can likely fix any that are found. Note that repairing air conditioner refrigerant leaks can be expensive.


  10. SpeedRacer220 | | #14

    Thanks. HVAC contractor came today and wanded a bunch of things and did a checkup. No dice. No carbon monoxide. Blocked the fireplace and nothing seems to have changed for me. Nausea and headaches continue though perhaps a tad better today.

    I am honestly out of ideas. I wonder if there is a weird pressure shift in the basement? My symptoms are more consistent with the gas leak type stuff but none to be found.

    1. Expert Member
      Zephyr7 | | #17

      A pressure differential is extremely unlikely since no matter how airtight you try to make your house, it will always leak and equilize the indoor pressure with the outdoor pressure. That's why weather station barometers are usually in the indoor unit and not the outdoor unit -- indoors is safer for the equipment, and makes little difference in the measurement. I'd be VERY surprised if there is a pressure differential causing problems for you.

      I'm going to recommend you check Michael's line of thinking here, and check the lights. Certain lights flicker just right and can cause headaches. This wasn't a problem with incandescent lights, but it can be with compact flourescents and some LEDs -- especially when operated on a dimmer switch. Flicker can cause headaches without your realizing why you're getting a headache.

      I have seen one oddball air/sound pressure issue. I had one commercial property I was involved with some years back with a big generator (1 megawatt) in an indoor generator in a room on the corner of the building. There was a neighboring building not far (maybe 20 feet) away. There was some kind of resonance when the generator would run, and if you stood in certain spaces between the two buildings it was nearly unbearable -- huge headache. As soon as you stepped a few feet in either direction, it changed from hugely uncomfortable to just "loud". There were several spots like this, so I know there was some kind of sound wave diffraction pattern, but I never tried mapping it out. It's possible if you have anything that runs at a low frequency sound (air blowers are most likely in a home), you could potentially be getting some constructive interference if the sound is reflecting off of a masonry wall that might make certain areas very uncomfortable to stand in. To test this, shut off anything that makes sound and see if the problem goes away.


      1. SpeedRacer220 | | #18

        Thanks for that information. As to the lights, I am often down there without any lighting because it is a walkout backyard, so we have big windows that provide natural sunlight. I will mess around with the lighting to see if that triggers anything.

        I like the idea of the sound pressure too. Let me turn off the furnace and see if that changes anything for me. Furnace was not on during the dusty renos. If that is it, that would solve a problem but also create one.

  11. Hammer 🔨 | | #15

    You mentioned in a large space you have wood panels. Some wood panels can contain formaldehyde, laminated wood does, also pt wood gives off chemicals. It could be a gas you aren’t testing for. I also would still consider some kind of lighting or design sensitivity as a culprit. If you renovated with no problem it has to be something you added

    1. SpeedRacer220 | | #19

      I think this weekend I will see if I feel that way with my eyes closed. Not sure how else to test the design sensitivity.

      These wood panels have probably been there for decades. Instead of ripping them down, we decided to just paint them and worry about a bigger reno later. I have always thought it was the paint on the walls but have not been able to confirm. That same paint was used upstairs where I have no issue - but not the extreme bond primer. I think the painters left behind the can so I can give it a sniff to see what happens.

      I agree it may be a gas but not sure what other gas I should be testing for and how.

      I should add that VOCs in the basement are usually low - around 50-80, except when airflow is bad. If it was paint, I would guess these numbers should be higher?

  12. SpeedRacer220 | | #20

    Hi everyone,

    I now think I may have figured it out but wanted opinions of this knowledgeable crowd.

    I forgot to mention that before moving in, we removed asbestos tiles in the basement and left behind mastic. Since I have kids, I was very concerned about that but all the abatement companies said the best thing is to cover it with new flooring. I must have confirmed that with four different companies.

    In my first post, I mentioned the floor we used and the underlay. My suspicion now is that the underlay isn’t letting the concrete breathe and that has created issues. Either that or the underlay is doing something with the mastic - I don’t know.

    The reason I think something funny is happening with that because there are rooms in the basement without the mastic and flooring and I am pretty sure I don’t feel the tense headaches there. I didn’t come to this realization until yesterday. I even have a room where I used the vinyl floor but that sits on top of plywood (that was there before), and I don’t think I have health issues.

    Does this make sense to anyone? I am thinking I have to remove the underlay and to replace it with the DMX underlay (which I only just learned out). Does anyone think I need to seal the mastic with anything or clean it (not sure how). Oddly, the laundry room in the basement (concrete) has mastic but my wife wanted ceramic tile and I don’t appear to have issues in that room.

    Thanks for continuing to help me. It has been a real drag especially knowing that kids are in the house.


    1. Expert Member
      Malcolm Taylor | | #21


      These types of environmental sensitivities are extremely challenging to diagnose and remediate, especially when they only affect certain people in the space. They are often resistant to the types of testing commonly done, and the only solution is to remove and replace a series of things until the instigator is found. I hope you are able to do that without too much more disruption.

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