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Ask the Carpenter: Dealing with rusty wood stoves, terrible smells

Ask the Expert Home Improvement

Q. We have a wood stove insert with rust on the top, probably caused by water from our humidifier’s cast-iron pot. Is there a way to remove it?

ANDREA C., Hanson

A. It is not at the point where you need to sandblast off the rust. Try removing the rust with steel wool or 200-grit sandpaper. Vacuum the area, and then rub on Rutland stove polish, which is used in the preservation and restoration of cast-iron and steel stoves and grills.

 

Q. I have a 50-year-old, four-bedroom Colonial with central air conditioning upstairs only ­— in two bathrooms and four bedrooms. About six weeks ago, we noticed a foul smell like rotten eggs in one of the bedrooms. I had two general contractors check it out, and neither could pinpoint the source. I had an exterminator check it out. He ruled out dead rodents. I had an HVAC guy come three times. He found nothing, but at my request he replaced the tubing to that room and put in an air freshener. The smell is still there. I blocked the AC vent with plastic, and the smell went away. When I remove the plastic, the smell comes back. We have no gas in the house. There is nothing in the attic except the AC tubes. All have been looked at. We took everything out of the bedroom and the closet. We cannot use the bedroom and have no idea who is left to call. What could it be, and how do we fix it? What kind of repair person should we contact? You are our last hope!

DIANE CARROLL

A. I’m not an HVAC expert and defer to those who have inspected your system; however, I did reach out to my HVAC contractor, Gerry Esposito from Central Air Systems, who told me that a rotten egg-like smell is usually sulfur. The duct to that room or the diffuser box may be reacting to something, he said, but he was only guessing. I would ask your HVAC professionals to look at that possibility.

Dear Rob

From Mark Garvey in Concord, who owns an air-sealing business: Regarding your response to the homeowners who can smell their basement when the fan on their forced-hot air heating system runs (“Ask the Carpenter: Replacing a rotten sill plate,’’ Sunday, Oct. 13) . . . A fresh-air intake is one solution, but I believe the smells are the result of duct leaks on the return side. When the HVAC fan is running, the negative pressure in the duct allows the basement air, which is at a relatively higher pressure, to get sucked into the duct. Then it is distributed through the house, along with its smells, on the supply side. A fresh-air intake to the HVAC will only dilute the smell. To repair (not always easy), seal all of the seams on the supply side with duct mastic, (not duct tape, which eventually fails).

From Bill Granton of Energy New England: I’ve worked in energy efficiency for 35 years, inspecting more than 20,000 homes and businesses. The cold air-return vent is probably leaking basement air into the system. This can also lead to a backdraft in which flue gasses are pulled down the chimney by the cold air return, which can be a carbon monoxide risk. My advice: Seal all of the ductwork.

Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @robertrobillard. Subscribe to our free real estate newsletter at pages.email.bostonglobe.com/AddressSignUp.