We moved into a new home in March 2008, ranch with walk out basement. The lower level has an odor which I can't really describe, the closet would be wet cement. The odor is not going away even tho I open windows and doors all day. I've used different types deodorizers, nothing helps. The basement is partially finished, and at this point is unuseable.
The builder says he can't smell anything; their salesperson says a new home odor. After a year the odor is still here.
Odor issues are almost impossible to troubleshoot without being onsite to personally experience the odor. The potential causes of odors in homes are almost limitless. Just to name a few that I have come across:
New material off-gassing. When new building materials are installed the components often off-gas chemicals that were used in the manufacturing process for some time. Usually, these dissipate over a period of a few days to weeks to the point that they are not noticable anymore. However, some may linger for YEARS because they have a low volatility and off-gas extremely slowly, and have a very low odor threshold (meaning a little bit can stink a lot, for a long time). Usually increased temperatures will promote an increased rate of off-gassing so the intensity of the odor may seem to be correlated with increased temperature in the space, or solar exposure to the room. A very basic way to gauge if this may be the problem is to close all the doors to the basement area so there is no air exchange in the room, and then either turn up the heat, or let the sun bake the room if there are windows and it gets solar exposure. Go in there after several hours and smell. If the odor has intensified, then it could be offgassing from building materials. Do a control experiment too by keeping the room airtight, but keeping it cool, and see if the odor intensity decreases. Tracking down the offending building product can be an arduous task - take small pieces of each component (ie a little bit of carpet, a little bit of insulation, a little bit of drywall, a little bit of ceiling tile) and put them in plastic ziploc bags. Warm the bags up, open them, and sniff. Does one mimic the "Basement odor" If so, that would be the most likely materal to start removing and see if the odor goes away. These types of odor complaints are never easy to solve.
Sewer gas - I've seen unsealed or poorly sealed sump pits that give off nasty sewer gas odors. Do you live in an area with a combined sewer system? Or is your sump storm-water only? Check to make sure the metal lid on the sump is sealed airtight with a bead of silicone caulk beading around the perimeter, and also around the perimeter of any holes going through the center of the cover for water ejection.
Mold - it's an extremely common cause of basement odors. If there is any chance your house has sustained water damage in the basement, or was open to the elements during construction after they installed wood framing and drywall - you could have hidden mold growth. The easiest way to tell is to physically check. Cut a hole in the base of the drywall/wood paneling / (whatever wall materal you have), and look at the back side of the material. Also pull out some insulation from along the bottom and look at it. Lastly, inspect the wood 2x4 framing. It should all appear clean. If there are any circular spots (black, white, green are common color for mold) then you have mold growth. Hidden mold growth will emit microbial volatile organic compounds (mVOCs) which are a metabolic byproduct of the mold "living and breathing" - and this is what we smell and characterize a moldy area as having a "musty" odor. If you have moldy materials, the best solution is to rip them out and replace with new. Best to get a professional mold remediation contractor involved if the amount of mold affected materals are more than 10 sq ft.
Urea formaldehyde insulation - Can give off a "urine" like odor when it gets wet. What type of insulation did your builder use? This stuff is not common in new construction, but good to ask.
A few more comments...
Of course the builder and sales-person will play it off as "no problem" or "we cant smell it". Would you expect anything less from them? Get an uninterested 3rd party involved. There are many professional environmental consulting companies that specialize in odor assessments like this. They have expertise, and also have specialized testing equipment that can help peg down the source of the odors.
As far as deoderizers - all they do is mask the odor. The odor source is still there. A standalone air filtration unit (HEPA filter!) **MAY** help the situation. It's worth a try. Still, it does nothing to remove the odor source, but it **may** help remove the oderous particles present in the air so the problem is not perceived, or lessened. This would only be applicable if the offending "odor" is a microscopic particulate. If it is a gas, then a HEPA filter will do nothing for that. A charcoal air filter will help capture some common odorous gases, but they are very expensive and need to be changed out very frequently, at least monthly, or else they loose their capacity to absorb chemical gases from the air. AVOID any air "purifier" that "emits ions", "ionizes", or emits "ozone". These are BAD products that can actually worsen respirator irritation and cause other problems. HEPA filtration and/or carbon/charcoal filters are safe and effective methods of cleaning indoor air. If you get one of these, make sure it is SIZED appropriately for the room you place it in. The product box should say what size area the unit is effective for. A cheap $50 unit that treats "up to 250 sq ft" obviously would be a poor choice for a 1,000 sq ft basement! Expect to spend $150+ on a good unit.
That said, finding the odor source is really the ultimate goal. Any air purification solution is really just a band-aid covering up the problem.
Good luck hunting down the odor. These things are really tricky! Get a professional onsite if you can't figure it out with my list of common offenders I gave above.