An attached garage is a great convenience for homeowners, but it can also be the source of indoor air quality problems in the house.

Garages are prime areas for pest entry, because overhead garage doors don't always fit tightly at the bottom or the sides. There may also be another opening to the exterior (such as decayed trim at the door casing). Then mice and shrews can find their way through holes and gaps from the garage into the ceiling and wall cavities of the house. There should also never be exposed fiberglass in a garage, because

insulation is a favorite nesting place for rodents.

I often find mold growth on the back of overhead garage doors, because these surfaces are cold, resulting in condensation or high humidity. People often use a garage for storage, and items that are leaning up against the cool walls, and boxes sitting on the concrete floor, can become covered with mold.  I also sometimes see an extra refrigerator in an attached garage, and the gaskets as well as the sides can be covered with mold. In snowy conditions, people drive a car into a garage with the wheel wells covered with snow. When the snow melts and the moisture evaporates, the relative humidity of the garage air increases, which can result in mold growth on cooler surfaces.

* Paints, varnishes and pesticides stored in a garage can be sources of VOC's (volatile organic compounds). Gasoline-powered equipment can leak, and a gasoline-powered mower or snow blower, if started in a garage, can produce combustion products, including surprisingly high concentrations of carbon monoxide. If there is habitable space - such as a family room or master bedroom - above a garage, it's important to warn your client about leaving any gasoline engine running inside the garage.

* If you are inspecting a property with an attached garage, here is some additional advice you could offer your client, depending on what you see:

* Store paints, varnishes, and pesticides (including fertilizers, which often contain pesticides) in a separate building, such as a garden shed. If this is not possible, be sure the lids are tightly sealed, or store these materials in metal containers with tightly fitting covers.

* Don't keep leaking gasoline-fired equipment in the garage.

* Seal up any holes or gaps around pipes, electric cables, etc. that could allow pests to travel from the garage into the house.

* Be sure overhead garage doors close tightly; add sweeps or gaskets as needed.

* Any garage door leading to the exterior or into the house should close tightly; again, add sweeps or gaskets as needed.

* To avoid attracting pests, don't store birdseed or pet food in a garage.

* Kick snow off a car's wheel wells before driving the vehicle into the garage; this will also keep salt out that can cause damage to the concrete (if the property is new construction, recommend having the concrete sealed).

If there is a mold problem in the garage, the space could be dehumidified in hot and humid weather.

* If the garage is to be used for storage, recommend that goods be placed on rolling metal shelves.  Nothing biodegradable should be placed on the concrete. Keep clutter at a minimum.

* If there is a furnace in the garage, make sure that the return system is airtight.

* If there is a warm-air supply in the garage, air from the garage is sucked into the system by convection when the blower is off. The register should be sealed, and an alternative heat source used for the space if necessary.

* Clean the garage on a regular basis.

To protect their own health, occupants should pay attention to garage conditions, because as far as the flow of air is concerned, an attached garage is part of the house.

Happy New Year to all.

Jeffrey C. May