Q. Our fireplace was converted to gas logs many years ago by the local gas company, which has been sold multiple times since then. The installation went unserviced until this winter, when we couldn’t light the logs. I should note that over the years the unit has been rarely used, and the gas is turned off in the basement until we plan to light the fire.

The serviceman from a local fireplace/stove dealer did extensive cleaning and said there was a fair amount of rust. He introduced a note of concern about using it and strongly suggested that we buy a carbon monoxide detector for the room. He instructed us to install it just a few feet above the floor for optimal protection. We did. (The instructions, however, said just to install it on a wall.) We also have a carbon monoxide detector on the second floor and one above the stairway in the basement.

S.D.

A. To quote you: “He introduced a note of concern about using it and strongly suggested that we buy a carbon monoxide detector.’’

That is a clue for us detectives that this unit might be dangerous. I strongly suggest you get a second opinion and consider replacing it. It’s super cheap insurance compared with a fire or carbon monoxide poisoning.

Q. We put rigid insulation all around the exterior foundation of our home. What is your favorite way to finish this so it doesn’t look awful? The options we’re considering are stucco, stone veneer, and sheet metal (copper, probably).

The metal options seem to be the least offensive. Stucco and stone veneer both seem to have permeability troubles. Also copper looks really nice.

Also, how do you feel about carbon monoxide vents for garages?

ALEXANDER, Dorchester

A. I’d recommend a metal cladding like aluminum or copper coil stock. My favorite pick would be copper, provided your budget allows.

As far as the carbon monoxide vent in your garage . . . I have to ask why? Are you running your cars in there? Doing mechanic work?

These are passive vents with adjustable louvers that install directly into the garage door. In the open position, the vent allows air to move in and out. I suggest you check out this study from the University of Iowa on carbon monoxide poisoning and garages: www.abe.iastate.edu/extension-and-outreach/carbon-monoxide-poisoning-garages-aen-207/

I love rules of thumb, and here is one you might want to consider for required air changes per hour: The minimum number of air changes per hour in a storage garage should be least 4 to 6. The minimum in a garage or workshop used for repairs should be at least 20 to 30. Air flow is measured using a flow hood, an expensive tool used by HVAC companies.

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.