KEEP THE HOME FIRES BURNING
(BUT NOT THE HOME)
Picture this scenario, - you are out for a leisurely evening stroll, the leaves are changing colour, the air is cool with crispness associated with autumn and the aromatic scent of wood burning permeates the air. As you stroll past a home you glance through the living room window and see the reason for that aromatic scent, a fire blazing in the fireplace. It looks so tranquil and cozy, when suddenly you are startled by flames ascending into the sky some ten to twelve feet above the chimney top. You hear a sound similar to a jet aircraft passing overhead, a loud bang and as quickly as it began, it is tranquil with no visible signs of flames lighting up the evening sky. What happened? Was it a shooting star? Was it the Canadian space shuttle Meecharoni lifting off on another tour of the universe? Neither. What you witnessed was a chimney fire. Most chimney fires do not end so quickly, they usually continue to burn out of sight, unknown to the occupants.
According to figures released by the Ontario Fire Marshals Office for the year 1986 there were 625 chimney fires related to solid fuel (wood) being burned in residences. There were a total of 1213 responses by fire departments in Ontario that same year due to wood burning devices in residences. It is alarming that more than half of these responses were due to chimney fires in homes. IS a chimney so difficult to maintain, or is it that we as home owners and renters are negligent in our maintenance practices? Perhaps we simply take it for granted when the smoke continues to exit the chimney rather than into our living rooms. Why should we repair something which does not appear to be broken? Let us return to our scenario and determine what we saw and why did the flash of flames and mini explosion occur.
When analysing chimney fires it is important to remember that there are a variety of reasons why they occur. It may be because of cracks in the brick or mortar, improper installation, or creosote build-up.
At this juncture we will deal with creosote build-up, which is the major cause of chimney fires in Canada.
In order for a fire to ignite we must have a combustible material and in this case it is creosote combined with an unknown source of ignition. Creosote is a byproduct of solid fuels such as wood, which creates tars and alcohols that adhere to the interior of your chimney. These wood tars and alcohols condense on the cooler surfaces of stove pipes and chimney flues. They begin as a dark brown sticky liquid which you have seen seep out of elbow and chimney cracks. It then dries to a semi solid and finally to either a flaky solid or a soot-like deposit. The longer creosote seeping through the connections and joints is not an indication of its absence. To determine the state of creosote build-up a simple tap on the flue will tell you whether it is time to have the chimney cleaned. When tapping the flue listen for a sharp clang or ring that will tell you that your chimney is clean. If you hear a thud, then it is time to call Dick Van Dyke, or your neighbourhood chimney sweep. Another major warning sign of creosote build-up is smoke backup, or bad draught characteristics. Should either of these situations occur, have your chimney inspected as soon as possible.
Three major factors that influence creosote build-up are inefficient burning of manufactured logs. The manufactured log problem exists more in the city, because of sotrage, convenience and very little ash in the firebox. These store bought logs consist of wood, paraffin, and other highly volatile products which help in the formation of creosote. Our advice is to limit the frequency of burning these logs and do not burn more than one at a time.
The ignition of creosote most often occurs when burning highly flammable debris such as paper, cardboard, and remnants of construction projects. Their burning time is minimal but they create a very hot fire with long tentacles of flame reaching into the chimney flue. Christmas and Boxing Day are notorious for chimney fires for obvious reasons such as burning wrapping paper and boxes.
The fireplace or stove in your home was built or manufactured as a heating/cooking device, not as an incinerator. Be cautious.
By the way, the loud bang which we referred to in our opening paragraph was caused by the expansion and cracking of the chimney due to the intense heat.
How often should a chimney be inspected and cleaned in order to prevent us from living through this fictitious scenario? Experts agree that it should be done twice a year, before the burning season (early September) and after the burning season (latter part of May). The reason for the first inspection is to ascertain that leaves or branches have not fallen into the chimney, also that birds or animals have not built a nest and clogged the opening.
The reason for the second inspection is to clear any accumulation of creosote and to ensure that the chimney is structurally sound for the upcoming burning season.
Should you require a specialist for any type of fire please call the writer and we will arrange for one of our Forensic Engineering Resolution Team experts to resolve your problem.
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Walters Forensic Engineering | 277 Wellington
Street West, Suite 800 | Toronto, ON M5V 3H2