17 Nov The Air in Here Smells Bad! What Can I Do?

Identifying the cause of smelly indoor air can be a complex process. The English language is not a good tool for describing smells and there is often little agreement about what an odor smells like, making it difficult for a professional to identify the offending substance from a description of the smell. To make identification even more difficult, there are tens of thousands of synthetic compounds and thousands of naturally created compounds that produce odors. Complicating matters still further, many compounds in the air are broken down by the natural process of oxidation to form new compounds. The new material may smell when the old one did not, or the new material may smell completely different from the original. Identification can be simpler with more common odors such as mold, gasoline, natural gas, or alcohol.

There are sophisticated approaches and instruments for identifying the chemical composition of an odor. Once the chemical is identified, potential sources can then be determined and the building can be searched for these sources. However, this approach uses expensive equipment in a lab, costs hundreds of dollars per air sample, and may require multiple types of samples.

Luckily, most of us come equipped with an exquisitely sensitive instrument — the nose! The human nose is incredibly effective for tracking smells. The olfactory sensitivity of most people is at a part per million level. In other words, people can smell one part of the offending substance in a million parts of air. A few individuals can detect odors at a part per billion level, the level normally reserved for animals such as dogs. So tracking the odor back to its source can be done by using your nose.

A word of caution: some strong chemical vapors can be a health threat. People who are already sensitive or allergic to smells should not be involved in this type of investigation. Other people should not continue tracking odors that become too strong to be comfortably tolerated. You should stop following solvent fumes, gasoline fumes, or natural gas odors when they become uncomfortably strong. If this happens, it would be a good idea to call for help and air the space out. Note that natural gas, propane, and other household fuel sources contain odorants to alert you if they are leaking. These gases are an explosion hazard, so if you suspect that a dangerous gas leak may be the cause of the odor, call for help immediately. The gas company will provide a free leak detection service.

If the entire house smells, it may be helpful to air it out first and then close it up again to see if the formerly pervasive smell can be detected closer to the point of origin. Because people experience what is called olfactory fatigue, becoming less and less sensitive to the smell with prolonged exposure, you may need to give your nose a rest from time to time.

Moldy smells are common. The source of these smells can sometimes be located by looking for places where water intrusion has dampened building materials, decorative items, or other household goods. Water intrusion can be located by looking for water stains on drywall, baseboard, carpets, or corrugated boxes stacked on a concrete floor. In homes built on a concrete slab, problems with water movement through the slab can cause mold growth in the carpet and pad, particularly along outside walls or under furniture with skirting that prevents air circulation. You may be able to smell this mold by getting close to the carpet.

Mold growth inside the walls that results from water intrusion can sometimes be located by removing the electrical wall outlet faceplates and smelling the air in the outlet boxes, particularly those mounted in the outside-facing walls. The smell from a moldy basement or crawl space will move upstairs because rising warm air exiting at the top of the house draws replacement air from the basement and through other holes in the building such as outlet and switch boxes and heating/air conditioning ducts. Also look for water leakage in cabinets under sinks. It is always prudent to call in a mold specialist in cases of suspected mold and I do not advise a homeowner to open wall cavities or baseboards. You can, however, lead the inspector to places where you have noticed moldy smells.

Less common but sometimes problematic are bacterial smells. An example is the odor of dirty socks, or locker-room odor. Wet building materials and fabrics in a home can create a problem with bacterial as well as mold growth.

Another approach to tracing an odor is to think about everything that happened prior to its detection. When did you first notice it? Did this coincide with something being brought into the house or a precipitating event? This might include one or more of the following:

• painting and decorating
• new clothing or household goods
• pest control treatments
• new furniture, carpeting, or drapes
• a change in cleaning products or housekeeping services
• new asphalt-type roofing, yours or neighbor’s
• significant rain, with or without high winds, causing building leakage
• house painting, yours or neighbor’s
• lawn treatments, yours or neighbor’s
• long periods of non-use for sinks, bathtubs, or showers, leading to drying of water in the drain trap
• spills or leaks that could enter your basement from nearby industries or gasoline stations
• septic tank wastewater system failure

The “house detective” process can be time consuming and lengthy, but you know your home better than anyone else. You can save time and money by giving the situation careful attention and thought before your professional arrives. If all else fails, you can call a specialist to help identify the source by collecting a sample of the offending air for lab identification of its chemical components. Good sniffing!