stinky basement which spreads upstairs when furnace/ac is running

[kpster]

We moved into a 2 story home a year and a half ago. I noticed the smell the first time inside this house and especially in the basement -kinda musty, cat pee? but not dead-animal smell. I figured it was due to the fact that the house had been vacant for almost a year, not aired out ect...

After we moved in and turned up the heat (thermostat had been set very low) the smell was quite strong. I noticed many rocks-in-mesh bags hanging everywhere in the basement- odor absorbers.
As a quick fix, I replaced these (they cost a fortune!) and the smell in the basement was improved with the upstairs smell better but not gone completely.

The furnace and hot water heater are blocked off in a room (long/narrow rectangle room) with louvered doors. The basement is very dry (we're up on a hill) and has no stale water, moldy smell or standing water. The furnace is about 5 years old, high efficiency.

So the smell is in the basement and travels up to the main floor thru the vents when the heat/ac is on. It's strongest upstairs when the blower initially runs and then tapers off. The basement always smells tho it's worse in damp weather. We put one of those aromatic furnace thingys on the filter (as per instructions) and it helps tremendously. That and the charcoal rock deodorizers make the problem much better but I'd like to make it go away, permanently not just cover it up and pay a fortune doing so!

I read another thread that suggested cleaning the filter grids? We have a removable/cleanable filter (by vacuuming,which we've done) The ductwork was "professionally" cleaned when the old owners moved out.

Where could it be coming from? Could it be in the concrete floor- like years of cat pee? Arrgh.
Any thoughts on this? Thanks!!
kpstr

[HayZee518]

those bags you speak of - activated charcoal?? is there any sort of drip pan underneath those bags? if yes, those bags contain calcium chloride pellets which attracts moisture. if you go for a ride in the country where there are dirt roads, sometimes you see the road crews spreading white pellets on the ground. this is calcium chloride which pulls in the humidity from the air and it moistens the dirt to reduce dust from the ground. CaCL2 was used before commercial dehumidifiers were made.

[kpster]

hmm. The ones that were already there had no pans underneath. The bags are 4x4 ish squares containing rocks. (i do believe charcoal) The bags have a grommet and hang from a nail. The ones I bought from a grocery store are the same. They do a great job absorbing the odor. The aromatic sheets for the furnace just mask the smell. Maybe I should try bagged charcoal in each vent? I keep thinking there must be an end to the cause of the smell sometime!?

[Frat-man-du]

Having an older home form the late 60's early 70's that had an unfinished basement and a previous owner with a dog and cat that lived in the basement during the day I can appreciate your predicament. At first I hung athe activate charcoal bags by the cold air return - this helped. Finally I power washed the concrete used muriatic acid solution to etch the floor and sealed with garage floor epoxy from a major paint vendor. tht was 3 years ago and I have since finished 3/4 of the basement (rest is workshop) and no more oder. Cost of the chemicals was $400 (expoxy is $$$$). Regular concrete sealer like Thompsons might work just as well and cost only $50 - depending on the size of the space needed.

[amazon.woman]

I have the same problem

I need to make sure to keep the humidifier going all of the time (even though my basement is somewhat dry too) and that also keeps the smell down.

Is there something that can be sprinkled on the dirt in the crawlspace to cut down on the smell? Like, lime or something? I know for a fact that my cat is using it as a giant litterbox. How do I keep him from doing that?

[Frat-man-du]

Most major pet stores carry something like Boundary or Border something like that. comes in a spray bottle and or gallon jugs. It has to be applied every so often but should keep domestic critters out. Lime might make the pet sick, or worse... - that is a whole different smell!

[LazyPup]

A couple years ago my mother moved into a new home, well, not a new home, but new to her.

Within a couple weeks we began noticing the same musty smell in the basement that you are describing. I searched the basement diligently for the source of the odor but to no avail. The basement was completely empty with concrete block walls, a poured slab and the wood floor joists overhead.

The entire basement was bone dry, not a sign of moisture anywhere, yet the entire basement had a foul mildew smell. At first I suspected it was the floor drains so I filled them with water then poured some cooking oil on top of the water to prevent evaporation.

There was a sump pump in the basement although there was no sign that it had ever operated, but just to be certain I pulled the pump and thoroughly cleaned the pit, then I put some bleach water in the pit to sanitize it.

I then opened the outside cellar door and set a fan to vent the foul air out

After about two hours with the fan the odor was gone so we closed the door and thought we had the problem solved. Silly me for thinking it could be that easy. Sure enough the following day the odor was back.

Mother hung a bunch of those little air fresheners in the basement but lets be honest here folks, air fresheners do not eliminate an odor, they just mask it with a stronger pleasant oder, either way, it still stinks.

I thought about the problem for a few more days, then it hit me. Generally the musty mildew or septic odors are caused by decaying organic matter but there was no sign of any decaying matter in her basement. Could it possibly be at a microscopic level and we can't see the source? I thought about that for a while then I came up with a solution. I got out my 2gal garden hand sprayer and put 1gal of water in it, then I poured in one quart of Lysol and shook it up real good. I then pumped the tank up and set the spray nozzle for the finest mist I could get and I proceeded to spray all surfaces in the basement, slab. walls and ceiling. For about two days it smelled like a hospital down there but once the Lysol oder dissipated all the odor was gone.

[Frat-man-du]

Good tip - never thought about Lysol.

[pgmr]

Sewer gas?

If you have any floor drains, perhaps the water in the trap(s) has evaporated, which will allow sewer gas to come into the house. I'd run water into each drain in the basement and if it's one that isn't used regularly pour a little mineral oil into the trap as well. The oil will float on the water and help prevent evaporation.

[HelpMan]

One of the posible causes could beexcess of humidity. It really stinks and helps grow mold and mildew which is really bad and dangerous.
I had many problems with mold and the first thing they told me to do is ventilate the rooms 10 to 20 minutes a day at least.
After that thy recommended me to use a dehumidifier but they were quite expensive and they consume a lot of electricity. I finally found a non electrical moisture absorber called HumyDry and it really works believe me. I think is calcium chloride or something similar...
I use it in my basement and the smell is gone. I use the big one for the basement and the small ones for the bathroom and closets. They also have fraganced refills. They say it last from 2 to 3 months but I have to change the refill every 40 days more or less.

Hope this helps!

[HayZee518]

if you read my post which is the second in this thread you'd see I already mentioned calcium chloride.