Correction: An earlier version of this story mischaracterized hot, humid air as being heavier than cold, dry air. This version has been corrected.

Q: How do I stop my wood-burning fireplace from smelling like smoke in humid weather? A faint smoke smell would be okay, but this is obnoxious. It seems worse when the air conditioner or even the washer and dryer are running. The smell just wafts on in from the chimney. We have a glass door installed, but it doesn’t help.

Burke

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 smoke-smell problem because our noses sense smells more intensely when the air is humid. 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. A&T Chimney Sweeps in Arlington (703-659-1699; atchimneysweeps.com) would do this for $629, said Veronica Campbell, the administrative assistant.

Or, for $42.99 to $86.99, depending on the chimney width, you could install an inflatable device known as a Chimney Balloon, available at Amazon.com. It has mixed reviews, however, with some buyers reporting that it punctures as easily as a water balloon. Filling a hefty plastic bag with insulation and stuffing that into the chimney opening at the base of the fireplace might work just as well and would surely cost less. 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 in your home. It might help to pipe fresh air directly to combustion appliances (which would include the dryer if yours is a gas model). Or you might benefit from a heat-recovery ventilator, which could introduce more fresh air but in a way that uses the temperature of indoor air to preheat or precool it so you don’t waste energy. Sealing leaks in heating and air-conditioning ducts or balancing the system by adding more openings might also be part of the solution.

Q: We have a KitchenAid Superba garbage disposal that 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. The blades rotate, chopping up the waste, but the waste does not exit the unit. I called the manufacturer for guidance. I was told to fill the disposal with ice to help with grinding. Although some relief was obtained, much of the waste remained in the disposal. Any ideas about why it is failing? Is it time to replace it?

Arlington

A: This is a three-fourths-horsepower model that’s still sold. It has a five-year limited warranty that would cover a repair visit to your home — if it were still in effect. But the warranty expired about 1½ years ago, a sign that it’s probably time to replace the unit. The current cost is $279 at Lowe’s and perhaps even less from other retailers if you shop around online.

If you’re reasonably handy, you could probably install a new unit yourself. KitchenAid provides installation instructions that appear straightforward. But if you want professional installation, Lowe’s would do that for about $120, said a spokesman at the company’s Beacon Center store in Alexandria (703-765-8011).

Before you resort to that, you might try repeating the ice trick a couple of times. Disposals sometimes work poorly because of a buildup of grease and other debris. 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 in its care manual: With the unit off, place a stopper over the opening and fill the sink halfway with warm water. Mix one-fourth cup baking soda with water and dump it in. Turn on the disposal as you remove the stopper. If you’re lucky, the force of the water, plus the bubbling action and grease-cutting properties of baking soda, will help restore the unit’s performance, as well as eliminate any foul odors. After the sink drains, remove the sink baffle and clean it by hand or in the dishwasher. Replace it before you operate the disposal again.