Gas log installation, vented or vent-free, in Meridian Park

How far the damper must stay open

A clamped damper still has to leave enough open area for the exhaust. One maker's table sets a minimum permanent opening by burner size and chimney height. With a masonry fireplace and 15 feet of chimney, it asks for 27 square inches with the smallest burner, 35 with the 24 inch and 41 with the 30 inch.

Factory-built fireplaces and taller chimneys get smaller figures in the same table. Our crew measures the actual opening once the clamp is fitted and writes the number in your record.

Why a log set smokes or soots

Smoke and soot from a gas log set have a known list of causes. One maker's troubleshooting table covers the chimney, the damper, the burner position, the media, the air openings and the logs themselves.

Our pros work through that list in order at your home, because the fix for a closed damper is nothing like the fix for a propane burner running on natural gas.

• Poor draft, downdraft or a closed damper
• Burner too close to the front of the firebox
• Media placed wrong or packed too tight
• Air mixer closed or air shutters blocked
• Logs out of position
• Burner built for the other gas
• Accessories that do not belong to the set

The oxygen depletion safety system

The state fuel gas code requires, in section 621.6, unvented room heaters to have an oxygen-depletion-sensitive safety shutoff system. On vent-free log sets, it is usually built into the pilot, often called an ODS pilot.

One vent-free manual explains that the ODS shuts the heater down if there is not enough fresh air and cuts off main burner gas if the flame goes out. A set that keeps shutting off is telling you something about the air in the room, and our pros never bypass the system.

Propane tanks stay outdoors

Propane log sets come with a clear rule about the tank. One vent-free manual says not to place propane supply tanks inside any structure and to locate them outdoors.

Tank placement and sizing are your propane supplier's call. Our pros note what they see during the inspection and point out anything that looks inconsistent with the manual, so it can be raised with the supplier before the set goes in.

Flames that start behaving strangely

A set that has run well for a while can change. One maker says that if the flames start to take unusual shapes or the burners fail to ignite smoothly, the burner may need cleaning or servicing.

Our technicians clean the burner and pilot, check the media and log positions and test the pressure. If the problem is a worn part, the estimate names it and shows whether a repair or a new set is the better value.