Don’t know where you are but here in Arizona we all seem to have at least one drain in the house that reeks. Because of the heat and lack of humidity, we have to top off all pea traps in the house regularly. All sinks, toilets, drains, etc that aren’t used daily have to have some water run to them to keep from drying out and letting the sewer gases through. Some people put soap or oil in those they don’t use often, to create a seal, to stop evaporation.

Our shower drain gets used regularly, but stinks. I put baking soda and hydrogen peroxide in, followed by boiling water after 10-15 minutes of letting it work. It only lasts a short period of time. We have resorted to covering it with a rubber drain stopper.

Animals in a crawl space or attic can also cause smells.

I would wonder what is under that landing at the bottom of the stairway. Remove the carpet, and pry it apart and check it out. I wouldnt be surprised to find, that something there was causing it. I see it also goes to the outside wall, so animals could be getting in there, or even water, and other. All that baking soda and its not helping anyway. You dont camoflauge smells, you track them down to the source and repair the problem, rather than covering them up. If it is something dangerous in the air, you are breathing it every day, and all the baking soda or house spray etc, is not removing it from the air you are breathing, even if it does camoflauge the smell.

Haha. I got halfway down reading your post with a certain response in mind, and with one of your closing sentences you confirmed it. Now I too have ”who you gonna call” running thru …….

edited to add: I took another look at your stairwell picture and noticed that houseplant setting in a pot inside a pot. Are you sure the smell isn’t coming from that? There could be rancid water in the outside pot that will stink.

bsgibbs--the only drain that doesn't get used is the downstairs shower and I run about a gallon of water down it regularly. I'm in Alabama and humidity is our non-profitable commodity. :)

The HVAC guys took a video of the attic and crawl space. No animal in the crawl space and no way an animal could get in the attic... there are no tree over or near the house. The smell moves too much for that too. I would have to have a herb of dead animals in the wall.

cat_ky---I saw what was under the carpet when the new carpet went down. It's just a wood frame. Under the stairs is the hot water closet. There is no wet, damp, or smell in it. I am going to ponder this some more though.

littlebug--it's not the plant. All my plants are double potted and if they had wet feet, they would pretty much be dead. lol

The baking soda does absorb the odor, but not as good as it was. After all the checks from those I called out here, I started thinking the carpet was off gassing again so putting down baking soda and vacuuming it off after at least 24 hours would help get rid of the gas before it hit the air (my theory). But then the cigarette smoke started--like the baking soda was dividing the smells--keeping one at bay and then another was predominant. I was thinking about buying an ozone machine or a hydroxyl machine. I just don't understand how after a year this suddenly started. It seems like the more I get fixed and painted, the more the house rebels.

Look into Thirdhand smoke

Cat_ky — thats about smelly water. The water doesn”t smell.

Shirlpp—you may have hit the nail on the head. I”ve never heard of that before but what I just read, could be it. Thank you! I”ll update in a few days after do some serious painting.

Before you paint you want to seal with a sealing primer, such as Kilz Original. Otherwise the contaminants will bleed through your paint and you'll be back where you started in a few months.

ramona -- I have a can of Zinsser Bullseye 1-2-3 primer already, and the paint I use is an eggshell paint with primer. It's my go to solution for walls that argue with me. This house likes to argue with me a lot.

New development--the toxic smell in the bathroom was also in the kitchen this morning. I had a piece of the carpet down at the kitchen sink as a rug. There is a closet in the bathroom that I use for a utility closet and there is a rolled up piece of the carpet in there. That door stays open because the bathroom is not used. I use the sink and toilet and run water in the shower. I got rid of both pieces of carpet and the smell stopped (not holding my breath though). Odors started in the living room around 9:45 am. Just eliminating things--I turned off the breaker for the hot water heater and turned off the HVAC to keep the smell from spreading through the house. Nothing changed. The smell in the living room did become more smoky though. I aired out the house and turned the AC and water heater back on. As I was taping the carpet, I smelled acetone-ish, and this time could smell it on the wall. I Googled thirdhand smoke last night as shirlpp suggested. I know the last occupants were heavy smokers. Looking at both cigarettes and E cigarettes, E cigarettes have formaldehyde, acetaldehyde, acetone, and liquid nicotine and cigarettes have nicotine, a form of cyanide, arsenic, polonium, carbon monoxide, lead, ammonia, etc. All of that can soak into sheetrock.

"Results of a study published in 2021 found that nicotine from thirdhand smoke reacts with the ozone, nitrous acid and formaldehyde to generate carcinogens..." and " “Homes become reservoirs of tobacco smoke pollutants,” Matt said. “These volatile compounds soak into the drywall; gypsum is like a bottomless pit for these toxins. Carpets are tremendous reservoirs.”

Considering the paint on the walls is builders grade flat, there is nothing to stop all that from embedding in the sheetrock. I had all the carpet and padding replaced, and I think I am dealing with more off gassing from the new carpet, but I think the bulk of what is happening here now is coming from the unpainted walls.

It's still early so... I'll see what tonight brings.

I found out that air purifiers without a carbon filter can re-release VOCs back into the air. I think putting the carbon filter in the return vent was good and buying the carbon pre-filter for the HEPA filter was good... I had two days of only smoke smell and it was not so bad. The carpet off gassing woke me up at 4 am and the entire house smelled of that chemical smell. Needless to say I reapplied the baking soda to the carpet and have the AC off and windows open. ugh

We had a bad, sulfurous smell when a battery in our generator was dying.

After having a plumber out and all was well with all things plumbing, I have to accept that the smells are from the sheetrock and carpet off gassing. The smoke smell is no longer a problem since I got the stairwell wall painted, but the carpet continues to be a pain. I did a bit of Googling about what carpet off gassing smells like and it is exactly what I tried to describe to people.

"This odor may be associated with formaldehyde, benzene, toluene, and a compound present in most latex carpet backings called 4-PCH."

"4-PCH is formed during the polymerization of styrene-butadiene glue used to attach the carpet backing on the pile. 4-PCH can further react with ozone (O3) in indoor environments and produce formaldehyde (a nasal irritant and known human carcinogen)."

"Benzene has a sweet, aromatic, gasoline-like odor.."

"Toluene is a colorless liquid with a sweet, pungent, benzene-like odor which provides an adequate warning of hazardous concentrations. Toluene is volatile, readily producing flammable and toxic concentrations at room temperature. Its vapor is heavier than air and may accumulate in low-lying areas."

"Formaldehyde is a colorless chemical with a strong pickle-like odor that is commonly used in many manufacturing processes."

The fact that I used a waterproof carpet padding adds to the problem because it too off gasses. Why it started off gassing so strongly a year later is beyond me, but since I seem to have bought really great carpet and padding, I'm paying for it now. There's sarcasm in that sentence.

Thanks to everyone who pitched in ideas because they gave me something to look into and eliminate. :)

After the 4th HVAC company I hired, they found the problem. The evaporator coils were coated with so much nicotine that it looked like a giant honey comb dripping in honey. All the people who said they crawled under the house did not. The 4th did and showed me the pictures of what he found. He was also covered in red clay. I never noticed the others were not. He blasted that bugger clean and the thick foam insulation within the return register. The change in the air was immediate, considering, and over the next few days got better and better. I have not had a problem with that smell since. It was funny because I don't smoke but every now and then would crave a cigarette. I now have a security camera over the back of the house so if someone says they crawled under the house, I can look and see if they actually did. The money I spent because of lazy HVAC people is insane.

Funny you mention security camera. I had a similar problem that was solved by a ring camera. In my case the odor smelled like molasses and like your odor, came and went . One day while reviewing ring footage I noticed a couple of little moles entering and leaving house at random times.