Shower smell: Check the bath fanIf you can smell that moist, shampoo-scented air from the shower and you are not in the bathroom, then you either don’t have a bathroom exhaust fan, it’s not on, or it’s not powerful enough.Unvented bathrooms can cause your home to rot from the inside out — costly and bad for your health. Put in a bath fan if it’s missing (see GreenSpec guidance on bath fan selection), and get the electrician to have it come on with the light or with a humidistat. Attic smell: Air leakage problemsAttics smell different: it’s some combination of the insulation, the wood dried to a crisp by the summer heat, and probably some history of squirrels, mice, or both.When I smell this in the upstairs of a house — not in the attic — I read it as a telltale sign of extreme air leakage: lots of holes in the basement and attic floor that allow air to leak out, and to move in the other direction on some windy days. Solution: seal up the air leaks in your home, particularly between the attic and the living space. (See GreenSpec guidance on products that help form a home’s air barrier, and recent posts on where to look for air leaks in existing homes.) Basement smell: Dampness, leakageIt’s alarming when you can smell that musty basement smell on the first floor. Even the basement should not smell that way — if it does, work on improving exterior drainage, putting vapor barriers over damp walls and floors, and dehumidifying, among other things.If that smell is migrating upstairs, look for air leakage from the basement up through plumbing and electrical penetrations, and moisture problems migrating up from damp basement walls through sill plates. Check the bottoms of exterior walls for signs of mildew or mold, and manage the water at its source. Combustion gases: Safety issueIf when inside you smell the exhaust from your wood stove, furnace, boiler, or other combustion appliance, your health may be in jeopardy from the particulate matter in the smoke, or from carbon monoxide (CO) — which is odorless but often accompanies other gases. In all these cases, bring in the appropriate technician as soon as possible (the fire department may also be willing to measure CO levels for you), particularly if you’re due, in case there is an immediate problem with the heating appliance.If you only smell these smells on a windy day, or when a low-pressure system has settled overhead, the issue may be that the normal weather patterns that help gases exhaust from the home are working against you. This topic is more than we can delve into today, but if it’s a regular occurrence it is worth investigating with a contractor’s help. One quick point: if it’s a building with a high-capacity range hood, beware of “depressurizing” your home with that fan, leading exhaust to get pulled into your house from your furnace.Do you have carbon monoxide detectors? Why not? Kitchen smells: Install a range hoodSometimes it’s nice to smell what’s cooking all through the house, but in the long run it’s bad for indoor air quality, particularly due to the moisture generated by cooking. Install a range hood and run it when cooking, but look out for problems with high-capacity range hoods. (See GreenSpec guidance on kitchen range hood selection.) Dryer exhaust: Moisture, fire hazardSmelling dryer exhaust inside the house is a red flag indicating lack of a vent, or a plugged vent. Lack of a vent risks moisture problems inside your house, and coating everything with dryer lint.A plugged vent is a serious fire hazard. Take immediate action! Tristan Roberts is Editorial Director at BuildingGreen, Inc., in Brattleboro, Vermont, which publishes information on green building solutions. Stuffy smell: Need more fresh air?Does the building smell stuffy? Many homes and offices don’t have enough fresh air, for a variety of reasons.In commercial buildings, the most common problem is poorly designed or malfunctioning ventilation equipment. Calling in an indoor air quality expert or a commissioning agent would be wise. In homes, it’s likely that there is no ventilation system bringing in fresh air, and because of weather patterns or because the home is relatively tight, you’re not getting enough fresh air. A ventilation expert can help. Off-gassing: Keep harmful chemicals outTo maintain good indoor air quality (IAQ), avoid bringing smelly stuff into the house. If something smells bad, get rid of it. In the world of building materials there is a lot to keep up with here, but at a minimum look for low-VOC coatings, and other products with IAQ certifications such as Greenguard Children & Schools, and FloorScore. (See BuildingGreen’s guide to key product certifications for more info.)I’ve just scratched the surface here — keep your nose out and let me know what you’ve been smelling!For more information, listen to Joe Lstiburek’s indoor-air-quality podcast, and find out why your eyes, nose, and the back of your hand are surprisingly accurate IAQ diagnostic tools. A victim of a hepatitis E infection she picked up unknowingly in Brazil, Genevive Bjorn’s liver rebelled against her one night in Hawaii. Her body almost shut down on her, but with help from the hospital, a battery of tests, her watchful boyfriend at her side, and a diet of nothing but rice porridge, she squeaked through.This is what happened next, as she wrote last year in The New York Times: “My liver began barking at smells and substances I’d barely noticed before. I considered myself an earthy minimalist, but my house turned out to be a chemical minefield. I developed a doglike olfactory sense that guided me as I sniffed, recoiled and pointed out to Adam what had to go. He tossed out most of our bathroom and kitchen products, along with everything preserved or petroleum-based.”Her talent for nose for the faintest of smells makes her a “super sniffer,” one gifted with this sense. As Bjorn recounted recently on her blog, The Daily Smell, while sniffing around a friend’s new home at the friend’s request, she rapidly sniffed out the previous location of the kitty litter box which had been moved two weeks prior, rancid vegetable oil in the kitchen, possibly unsafe coatings on kids’ furniture and toys, and even the spot in the living room where the previous owner had died months before.You don’t need to be super sniffer, though, to pick up on scents in buildings that tell us some interesting things. Here are some that I’ve noticed.