Q: How do I stop my wood-burning fireplace from smelling like smoke in humid weather? A faint smoke smell would be OK, but this is obnoxious. We have a glass door installed, but it doesn’t help.

A: Chimney smells stink up indoor air when the air pressure is lower indoors than out. Especially in a house that was built to be fairly airtight, this can happen when a dryer or other exhaust fan runs or if there are leaks in heating and air-conditioning ducts. To equalize the pressure, air moves down the chimney, making your house stink. Summer conditions add to the problem because the outdoor air is hot and humid and therefore heavier than the drier, cooler indoor air.

In theory, closing the damper on your fireplace should stop the airflow where the air picks up the smell. But fireplace dampers often don’t seal very well. For a better seal, you could have a chimney sweep install a spring-loaded stainless-steel damper at the top of the fireplace flue. We called a local company that estimated the job at $630.

Filling a hefty plastic bag with insulation and stuffing it into the chimney at the base of the fireplace might work. Just be sure to remove the plug before you use the fireplace.

If closing off the chimney doesn’t stop the smell, call a heating and air-conditioning company to assess air balance. It might help to pipe fresh air directly to combustion appliances. Or you might benefit from a heat-recovery ventilator, which could introduce more fresh air. Sealing leaks in heating and air-conditioning ducts or balancing the system by adding more openings might also help.

Q: Our KitchenAid Superba garbage disposal was installed in January 2011. For the past few months, it has failed to grind up and flush vegetable matter that it previously had no problem with. I called the manufacturer for guidance. I was told to fill the disposal with ice to help with grinding. Much of the waste still remained in the disposal. Any ideas about why it is failing?

A: This is a three-fourths-horsepower model that’s still sold. It has a five-year limited warranty, but the warranty expired about 1?1/2 years ago, a sign that it’s probably time to replace the unit. It costs $279 at Lowe’s.

If you’re reasonably handy, you could probably install a new unit yourself. KitchenAid provides instructions that appear straightforward. Lowe’s could install it for about $120, a spokesman said.

First, you might try repeating the ice trick. Ice particles whip around in the mechanism and pick up the gunk, helping to clean it.

Also try another cleaning method that the manufacturer suggests: With the unit off, place a stopper over the opening and fill the sink halfway with warm water. Mix one-fourth cup of baking soda with water and dump it in. Turn on the disposal as you remove the stopper. The force of the water, plus the bubbling action and grease-cutting properties of baking soda, may help restore the unit’s performance, as well as eliminate foul odors. After the sink drains, remove the sink baffle and clean it. Replace it before you operate the disposal again.

Jeanne Huber is a freelance writer.