(Composed from more than 30 years of personal experience with solid fuel heating systems)
1. Wall pass-through thimble fires account for over 80% of house fires associated with wood burning stoves. For instance, after a devastating fire, I found that an 8-inch Fireclay thimble passing through a plank wall with only 1-inch clearance to the surrounding wood was the cause. NFPA code requires an 18-inch minimum clearance around any stove pipe. Using UL listed Insulated Thimbles allows a stove pipe to safely pass through a combustible wall when installed properly. I use the Insul-Flue™ or Heat-Fab® Safety Thimble™ in my installations and upgrades.
2. Unused thimble holes in chimneys are as dangerous as any breach in the chimney’s structure. This danger is often hidden by “pie-plate” covers, paneling, wall paper, and / or studded walls. While keeping with the NFPA rule of only one appliance per flu; often the result of removing a previously existing stove leaves a horizontal void that enables creosote to collect in the thimble that will eventually ignite and spread to the surrounding studs. The only safe solution is to plug the thimble hole with a UL listed plug. The Insul-Plug™ is an excellent product that provides an ultra-safe thermal barrier between the flue and combustibles; and prevents downdrafts from entering the room.
3. Inadequate Stove Clearances allow the intense radiant heat generated by solid fuel stoves to over-heat walls and / or ceilings above their combustion temperatures. Installing reduction shields made of non-combustible materials with a 1-inch clearance to provide ventilation reduces the required minimum safety clearance required between the stove and wall.
4. Inadequate Stovepipe Clearances are as much of a hazard as improper stove clearances. Single walled stovepipe should be no less than 18-inches away from combustible materials such as ceilings and walls. I use Home-Saver® Stovepipe shield, Superpipe™ Double-Walled Stovepipe, and / or HomeSaver® Mantle Shield in solid fuel stove installations and upgrades when clearance reductions are necessary.
5. Chimney Clearances must be flue-lined with 4-inch masonry walls at least 1-inch to surrounding combustibles. This is the minimum safety requirement; but sadly, most chimneys do not meet this requirement. Even a small crack in the flue can become a blow torch igniting surrounding combustibles in the event of a chimney fire. Installing a stainless steel liner such as Olympia® Rhino-Rigid™ is the most economical solution to a damaged flue or a chimney with inadequate clearances. In situations where the chimney is deteriorated beyond repair, we can replace the entire chimney structure.
6. Factory Built Metal Chimneys (Class A 2100HT SS) are an excellent choice if installed properly. However, being unfamiliar with the NFPA standards and proper installation techniques, many homeowners & contractors leave out fire-stops, flashings, thimbles and radiation shields; creating multiple hazards. At one structure, I discovered that the owner blew in cellulose insulation in the attic after the chimney was installed. While clearance to nearby combustibles was within spec; a fire resulted from the lack of ventilation and obstructed airspace around the chimney. The trained chimney professionals at Thomas Chimney and Stoves will inspect for these potential hazards.
7. Inadequate Hearth Clearances are a common and dangerous oversight. All wood & pellet stoves must have adequate, non-combustible hearths protecting combustible flooring. If the hearth is on a wood floor, extra protection may be needed such as heat shields, pedestal bases or extended legs. Fireplace hearths must have a minimum of 18-inches of non-combustible material extruding from the front of the fireplace.
8. Improperly installed Fireplace Inserts are the cause of many house fires due to creosote deposits behind the dampers. A stainless steel direct-connect is an economical solution to this hazard if the flue tiles are in excellent condition. The best solution is a full, insulation wrapped, stainless steel reline of the chimney which promotes draft, ease of cleaning, and reduced creosote buildup. Thomas’ Chimney and Stoves can inspect existing inserts to determine if they are properly installed and make necessary corrections.
9. Neglected Chimney Inspections and Routine Maintenance is a potentially dangerous incident waiting to happen. Frequent chimney maintenance is critical to avoiding fire and noxious gas hazards associated with all solid fuel and gas heating systems. At the minimum, an annual inspection by a qualified, professional chimney sweep of all chimneys and flue systems is a must. Improper operation of wood stoves (i.e. burning unseasoned wood; burning wood too slowly; and neglected cleaning of creosote deposits) rapidly produce fire hazards. A commonly believed myth is that chimneys serving pellet, gas, & oil appliances are maintenance free. The fact is; all chimneys are susceptible to blockages, tile degradation, and collapse which can result in smoke damage, carbon monoxide poisoning, and furnace blow-back. Many insurance claims can be traced back to an inadequate, poorly constructed, or a poorly maintained chimney system. These problems can be easily addressed by a chimney professional. Developing problems detected early are less costly to solve than chimney and stove problems allowed to grow unabated.
10. Failure to Meet Chimney Requirements for Oil and Gas Appliances is a major cause of problems such as furnace blow-backs, carbon-monoxide poisoning and smoke & soot damage to home interiors. In addition, newer Hi-Efficiency oil and gas appliances use power venting, direct venting, or even venting on PVC pipe because of low stack temperatures and high moisture content of their emissions. When connecting these more efficient units to older chimneys, the much cooler vented gases begin to condense on their way up the chimney causing acidic moisture to collect and assault the clay liners and brick structure; destroying the chimney from the inside out. Upgrading the chimney with a stainless steel, acid resistant liner as part of your High-Efficient gas or oil appliance installation will insure a safe heating system and will preserve the structural integrity of your chimney system for many years to come.
Wood stove and Chimney Inspections (Printable PDF file)