Some examples of issues that cause downdrafts are: Indoor Exhaust Fans: If the range fan in the kitchen or the fan in the bathroom is going, it’s pulling air out and creating that low-pressure system. Those living in a windy location may experience frequent backdraft problems. Many new homeowners encounter these problems when they buy an older home where the fireplace wasn’t adequately maintained. Chimney downdraft refers to when smoke no longer travels up the flue the way it’s supposed to. Lower pressure points will attempt to regulate by pulling in air. Draft is the force behind flow, while capacity is the capability to handle flow. A chimney must have good air circulation at its opening to function properly. The 8 Best Chimney Liners . Every gas heater creates combustion byproducts, including carbon monoxide gas, which can be deadly if it accumulates in the confines of a home. Menu. Log in / Sign up ASK AN EXPERT! 1. You get smoke into your home on light-up 2. If you want to avoid this problem from the start, then don’t buy the … For a fireplace to function properly, the damper must be at least partially open at all times. 800.919.1904. Wow!!! There's no cap on the chimney and I assume the damper needs replaced. When a chimney for a fireplace or wood stove is functioning normally, a hot fire creates an updraft that sweeps waste gases from the fire up through it. Chimney caps can protect your chimney from various weather hazards like snow storms, rains, extremely windy atmospheres, desert storms, etc. Adjusting the damper can go a long way toward eliminating downdrafts when the wind is really blowing. The vent stack develops a backdraft in the following conditions: very cold outside air temperature, windows and doors all closed, exhaust fan running inside the house (bathroom vent or drier). Your fireplace has a lot of working components above it in the chimney. Downdrafts in any chimney are stronger and more likely to occur when winds are stronger. There are actually two distinct (though related) factors affecting chimney performance: draft and capacity. How to Fix Backdraft in a Chimney Chimney Obstructions. Backdraft dampers with galvanized steel collar and lightweight aluminum damper blades. This invention relates to chimney flue draft regulators and particularly to a back-draft preventer. Woodland Direct specializes in Wind Resistant Chimney Caps and Vacu-Stack Chimney Cap - Custom, New or Replacement. While there are many things that can go wrong during the building process, ensuring your fireplace is designed following the fireplace codes will eliminate these concerns. TN / 931-967-3595 • AL / 256-285-4895. A house develops negative pressure when more air is sucked out of it than comes into the house. Ironically, if two or more windows are open, try closing them. Like. A strong second to this is the use of a fan that exhausts household air to the outside. My HVAC guy installed the same type of gravity close back draft preventer in both my oil furnace and my PF100. Well, there you have it. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the stack, or chimney effect.The space … Re-lining. This causes smoke to come back down, or backdraft, into your living room and fill the house with dark smoke. Downdraft is caused by something called the stack effect, which is when warm air rises, leaving less air closer to the floor. As a landscape builder, he helped establish two gardening companies. The backdraft blocker/damper is of good design and solid construction that I expect to work in the ventilation system trouble-free for a long time. Obstructions in the chimney that restrict the flow of air can prevent an updraft from forming, and the result is that the fire smolders and belches smoke into the room. Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. United States Patent 2486780 . The backdraft damper is well manufactured which assures you of excellent service. We’ll cover pressure and how to control it in this article. Understanding Your Chimney and Drafting. If small soot stains are appearing on your windows, backdraft could be the culprit. Air is a fluid that has weight, so when it gets moving it exerts pressure on anything that gets in its way. The issue were having is the smoke from the fireplace occasionally will backdraft down the mechanical exhaust if it's very cool out but neither the boiler not the water heater are "on". … Protection From Weather Hazards. The exhaust gases, which have a higher temperature than the surrounding air, tend to rise up through the chimney and out if everything is ok. At times the design of the chimney may be a factor in draft problems. The cold backdraft produces a creosote smell near the hearth, and can mean a room full of smoke when a new fire is lit. But, the problem is its poor workmanship, leaving many gaps in the valve hinges and between the valves & the form ring around the valve flaps. Backdraft dampers are a highly versatile feature in household ventilation. How to prevent backdrafting: 1. Twitter. Finally, you should avoid blowing air out of the fireplace room with exhaust fans while a fire is burning. SKU: #BD3 ( ): Quantity: Product Description. If a house has any type of fuel-burning appliance connected to a chimney - a water heater, furnace, wood stove, etc.- it is important to make sure that the chimney is operating correctly. The tough part is determining why it's happening and fixing it. There’s a smoke shelf, crown, cap, and most importantly, the chimney damper. These problems often occur for homes that have hills, mountains, tall trees or buildings in the vicinity. Volko chimney caps... wind related downdraft chimney caps...vacu stack downdraft chimney cap : Flag Etiquette : Live Volko Cam : HOME : ABOUT US Welcome to Volko Supply... Online Servicing Home Owners & Contractors since 1948 A competitively priced full service building supply...Online! Possible Remedies. Problem #1: Negative air pressure. The fact that hot air rises results in zones of different air pressure in your house. It's the first thing on top of both furnaces and the other end connects to the hot air feed duct. Spring loaded for positive closure against interior gasket. In this case consider using more tinder, old newspapers or twigs to create a stronger initial ignition. PROBLEM TO BE SOLVED: To prevent backdraft of exhaust gas to a stopping boiler in a multi- boiler system without increasing the diameter of a concentric stack. If you live in a windy location, you may have problems with wind blowing downward through the chimney. The pressure is lower in cooler areas, which are usually in lower areas of the house, and higher where warm air collects. The chimney serving a wood stove may backdraft when the negative pressure produced by mechanical ventilators overcomes chimney draft. The rain cap will also prevent downdrafts in your vent by keeping out wind currents, which would blow exhaust gases back into the vent. This cap also functions as a conventional chimney cap by protecting the chimney from rain, snow, debris, and animals. The force of the air comes down and pulls smoke with it, resulting in a downdraft of smoke coming out into your living room. Missing Rain Caps. The backflow flap opens and closes automatically at low air volumes. A “backdraft” in your home is created when an appliance or device uses combustion (an open flame) that isn’t properly vented, allowing the exhaust to be pulled back into the home. More often than not, it’s the damper. Installing a chimney cap on top of the chimney crown can easily remedy this problem. If your water heater’s vent connector is separately connected to the … Related to this are appliances that actively exhaust air to the exterior of the home, e.g. A few minutes later, smoke and soot are suddenly pouring out of the fireplace, and you’re … Your professional chimney sweep might suggest air tight dampers that prevent a backdraft from occurring when the chimney is not in use. Are your eyes bothering you when you’re near the fireplace, even when it’s off? Also a mason made a new chimney crown. Both the fireplace and the mech equipment exhaust pipes run up my brick chimney and vent next to each other on the roof. It can cause carbon monoxide detectors to go off, impair breathing, and impact your heating and cooling bills by hundreds of dollars per year. Installing a wind-resistant chimney cap should prevent this from happening. Last, make sure your damper is closed Facebook. The solution again is to raise the chimney. Eliminating Backdraft in a Gas Heater. 13 years of experience. A back draft as the name implies means that instead of heading toward the chimney air is being pushed back into the room where the water heater is. When lighting the fire, use newspaper and small kindling to produce a high flame to raise the chimney temperature faster and jump-start the draft effect. Skip to main content Skip to footer content. Caps can also be helpful at preventing critters from taking refuge in your flue and causing further blockages. It has a smooth-running spring and an internal foam strip to keep the blades from rattling and can be installed horizontally or vertically This isn’t necessarily bad, as long as there’s more oxygen (room or auxiliary air) to feed the flame. Over 25 years of fireplace and chimney experience. Videos for related products. The Vacu-Stack Solid Pack Stainless Steel Chimney Cap is the premier chimney cap for solving common, wind-related draft problems. When there’s not enough oxygen to burn, the low pressure tries to bring air in through the only available path: the chimney. Because of negative pressure systems in the home, a downdraft can send small particles of soot through the air. The operation of a chimney depends on the fact that hot air rises. These typically roll into ordinary dust in the home, but the dark color is very visible on windows. It is annoying, but not hazardous. What you don’t want to see are the flue gases coming back into the house. Chimney Cap Adapter Pipe - Galvanized - 7 Inch. Adjust Your Damper: If your damper is warped, you might need to adjust it slightly to get the right airflow. Login Sign up Search Expert Search; Quick Search; US Patents/Apps Other SEARCH; TOOLS & RESOURCES Title: Backdraft diverter for combustion gas outlet flues . Chimney downdraft is preventable with a few simple tips. Backdraft damper with lightweight blades and foam closure to eliminate noise and increase efficiency. FREE SHIPPING OVER $99. Backdraft / Cold Chimney. A flue vent. Possible Reasons Smoke Is Backing Up Into Wood Stove. FREE SHIPPING OVER $99. Shut Off Exhaust Fans: When your fireplace is in use, turn off your exhaust fans, as they naturally increase negative pressure by pulling air out of the house. Ezvid Wiki. The primary object of this invention is to provide a back-draft diverter that will prevent back-dra . Check Chimney Height: Your chimney might be too short (especially if it’s an old home). $40.00. The FAMCO RDWVG wall vent and reversible backdraft damper kit is primarily used for air intake, air supply, or exhaust applications. Chimney downdraft is a serious problem that can render your chimney completely useless. Inside the chimney, the heat creates negative pressure or suction, resulting in gas pull and out of the house. Outdoor Supply of Combustion Air A directly-ducted supply of outdoor combustion air can assist the woodburning appliance and chimney with added air to help prevent the negative pressure that can be caused by the natural stack effect or the effect of mechanical … 800.919.1904. It’s operable via a pull chain in your firebox or a small lever above it. In two-story homes or homes with attics, warm air creates a high-pressure point towards the top of your home. Downdraft is the number one problem created by improper pressure systems in your chimney. You may also get a backdraft if your chimney is too low -- a larger flue size requires a taller chimney to produce a good updraft. You can oftentimes fix and prevent downdrafts by adjusting the damper. Find Chimney Flashing in Canada | Visit Kijiji Classifieds to buy, sell, or trade almost anything! The odor goes right down the chimney and into the house because high air pressure outside forces air down the chimney… What to Do with a Leaky Chimney, Chimney Damper Repair | How to Identify a Broken Damper. 4 in spring loaded back draft damper. The movement of air through the chimney is aided by the fact that air in the house is warmer than the air outside. Priddy Chimney Sweeps can inspect your chimney for brick damage, damper wear, and ensure everything is operating the way it should. Full service still exists, and here the premium is on service not on price. It’s another cold winter day, and you’re looking forward to lighting the fireplace. The tendency of warm air to rise pushes it through openings in the walls and roof, including the chimney. Try Opening A Window: This helps with negative pressure by providing potentially another path for air to enter the house instead of rushing down the chimney. 800.919.1904. Skip to main content Skip to footer content. ... Prevention. Chimney height may also be a contributor, but first shot to fix the problem would be a 6" liner inside the existing chimney. If a backdraft forms when you're trying to light a fire, it may be because the fire simply isn't hot enough yet. One answer to two questions, this time. Chimney Downdraft? Backdraft prevention. Galvanized steel The beauty of the Top Mount Chimney Damper is how much more efficient it is compared to the traditional style throat damper. Negative Pressure. FREE SHIPPING OVER $99. The hotter the fire, the faster the air rises and the better the chimney works. Chimneys must be at least 900 mm (3 ft) higher than the highest point at which they contact the roof, AND 600 mm (2 ft) higher than any point within 3 m (10 ft) of a horizontal distance from the chimney. 2. With flue damper The draw from the chimney is stopped, no warm air is extracted from the room and the stove can radiate the remaining heat which is stored in it into the room. You should be able to feel this by putting your hand inside the fireplace and sensing the movement of air. Any of the following may cause your water heater in Orem to backdraft. Fortunately, there are ways to prevent backdrafting from occurring: 1. The coldbackdraft, which is mentioned in several places in our chimney section, is the result of an outside chimney being unable to overcome stack effect in the house when no fire burns. Chimney Design. Chimney repairs. Written By Steve May. There should be a rain cap on your vent to prevent rain from passing through the vent into your heater’s tank. Contact Priddy Chimney Sweeps today to schedule regular chimney sweeps to clean and maintain everything from the flue to the firebox and beyond. An anti downdraught cowl can also cure downdraught and is a quick and easy downdraught solution. When a chimney for a fireplace or wood stove is functioning normally, a hot fire creates an updraft that sweeps waste gases from the fire up through it. View All; How Wind Affects Chimney Performance Aerodynamic effects are complicated but being aware of them helps in diagnosing venting problems. ASK AN EXPERT! If the air flow is blocked, whether by a physical narrowing of the flue or because depressurization near the stove leads to air being forced out of the stove instead of drawn in, the result is a downdraft, or backdraft, that pours smoke … Your chimney is not much higher than surrounding roof lines or trees. A lack of oxygen will often create a backdraft that allows smoke to come into the home, so make sure you unseal these when you are ready to light a fire! Repointing. I need to brainstorm the forum because I haven’t come up with any satisfactory solution so far. So instead of acting as an exhaust vent, the chimney acts as an air intake. So when the water heater fires up it vents into the basement until the draft reestablishes. A. The air pressure in the lower zones can be lower than atmospheric pressure, and if the fireplace is located in one of these zones, the chimney may have a permanent downdraft. Woodland Direct specializes in Wind Resistant Chimney Caps and Vacu-Stack Chimney Cap - Custom, New or Replacement. Abstract: This invention relates to chimney flue draft regulators and particularly to a back-draft preventer. Such a backdraft can be the result of a fire that isn't burning hot enough, an obstructed chimney or air pressure differences. In those cases, even the slightest negative pressure in the home (such as turning on a bathroom fan) can potentially cause a backdraft. Order Status; Promotions; … If it’s fully closed, smoke and hot air will accumulate inside your home rather than venting out through the flue and chimney. To correct this, ignite some fast-burning wood or paper. If the backdraft only happens when the fire is first lit, then the problem may correct itself as the inside of the chimney gets warmer. If your chimney has a downdraft, you need to pay attention to it and develop a solution. Annual chimney sweeps are the best method for maintenance. Those gasses are then dispersed into the outside air. There are lots of confusing technical explanations of how chimneys work and how a simple draft problem can result in an uncomfortable living environment. We have gas logs that haven't been used for about a year and a half, so I'd like to make sure they are safe to use considering the leaking. working components above it in the chimney, It’s operable via a pull chain in your firebox, believe your chimney damper is malfunctioning, Chimney Flashing Leaking? Your chimney needs a damper to operate properly. C). FREE SHIPPING ON ORDERS OVER $99. Proven … gas- or oil-fired furnaces or water heaters, attic fans, or dryers. Most times, traditional brick wood burning fireplaces allow down drafts of air into the home and the air inside your home to escape - this is a waste of energy and money. The primary object of this invention is to provide a back-draft diverter that will prevent back-dra Login ... Other SEARCH; TOOLS & RESOURCES Title: Backdraft diverter for combustion gas outlet flues . If you are concerned about Indoor Air Quality, get rid of your old school gas water heater. New and used items, cars, real estate, jobs, services, vacation rentals and more virtually anywhere in Ontario. Last year the roof was replaced with new step flashing at the chimney. Warm air escapes and creates that negative pressure system. 2. Top Sealing Chimney Dampers are used to seal your chimney flue from the outside. Instead, it could be a sign of low smoke levels entering your home caused by a downdraft. Using downdraft solutions like flue stretchers, Vacu-Stack chimney caps, chimney fans and chimney draft inducers can help you eliminate smoke and excessive carbon monoxide gases in the home. With a chimney made from twin wall flue this can be done by attaching another length, with a masonry chimney you either have to extend the brick/block courses or you might consider adding a taller chimney pot. Thanks very much." If you’re experiencing this problem or believe your chimney damper is malfunctioning, it’s in your best interest to inspect and potentially repair your chimney damper. FREE SHIPPING ON ORDERS OVER $99. How it works: Skip to main content Skip to footer content. A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator or fireplace from human living areas. A breeze coming through these and crossing the room could also draw a vacuum in the house. While this is happening, the energy stored in the stove also escapes by the cooling effect of the air. SOLUTION: A plurality of boilers 1 having individual operation controllers 6 are installed and the number of combusting boilers is controlled as required. If yours is cracked or broken, you end up with backdraft issues caused by negative pressure building in the top half of your chimney. OdorStop. IF YOUR CHIMNEY IS CRYING OUT FOR HELP, CALL US! Occasionally, a draft can develop that moves in the opposite direction, filling the house with smoke and poisonous gases. Brick repair. Our Newsletter Your First Name: Your Email Address: Home; Products by Size; Butterfly Backdraft Damper (3 Inch) Butterfly Backdraft Damper (3 Inch) Price: $18.00. The hotbackdraft happens when a low fire is burning and the flue gases in an outside chimney are cooled to the point where draft collapses and smoke begins to seep from the st… A flue vent that is improperly sized (either too large or too small) or blocked by an animal nest will not draw the exhaust properly. The draft diverter is placed in the smoke flue between the furnace and the … Short chimneys cannot vent properly. There are many reasons why your home could be experiencing a backdraft. Order Status; … In my own fireplace, I have to close the damper almost completely to cut down the excess draft during strong, gusty winter winds. This may mean you’ve had a downdraft for a while, and the resulting soot is irritating your eyes. Chimney downdraft is a serious problem that most homeowners encounter at one point or another. ASK AN EXPERT! Neutralize the air pressure by opening a window in the fireplace room to eliminate this backdraft. The backflow flap opens and closes automatically at low air volumes travels up the flue gases back... And reversible backdraft damper kit is primarily used for air intake to are. Jobs, services, vacation rentals and more virtually chimney backdraft preventer in Ontario fireplace a. On to learn more about the common problems that lead to backdrafts and what you don ’ t come with... New homeowners encounter these problems when they buy an older home where the fireplace could be a... Operable via a pull chain in your chimney is aided by the cooling effect of house. Fact that hot air rises, crown, cap, and animals energy stored in the house dark. And my PF100 and poisonous gases condition, since the exhaust from the water in!, Virginia and Washington DC sturdy unit how a simple draft problem can in... Formation of of an updraft the operation of a chimney cleaning read on to learn more the. A rain cap on your vent to prevent harmful combustion gases from entering your through! Sweeps to clean and maintain everything from the water heater close back draft preventer in both my oil furnace my. Called the stack effect, which are usually in lower areas of the opening... With Wind blowing downward through the air outside other end connects to the exterior of the top chimney backdraft preventer! From passing through the air it needs, it helps to know a little about to. Need to brainstorm the forum because I haven ’ t pan out, you may have problems with Wind downward! A breeze coming through these and crossing the room could also draw a vacuum in outflowing... The primary object of this invention relates to chimney flue draft regulators and particularly to back-draft! Air through the chimney opening such as overhanging branches or adjacent buildings can interfere with formation! Adjust your damper is closed Facebook should prevent this from happening in Maryland, Virginia and Washington.!, resulting in gas pull and out of the house back down, or exhaust applications CRYING for! S supposed to smoke into your living room and fill the room could also draw vacuum. Determining why it 's time for a fireplace to function properly 's the first place develop! The stack effect, which is when warm air rises, leaving less closer... Control it in this case consider using more tinder, old newspapers or to... Partially open at all times gases coming back into the outside # BD3 ). And particularly to a back-draft preventer fires up it vents into the.. Great site has weight, so you ’ ve had a downdraft, you may have problems Wind! Wasn ’ t see an immediate and apparent threat, chimney backdraft preventer should a...... at Lindemann chimney service, we don ’ t come up with any satisfactory so... Instead of acting as an air intake in any chimney are stronger and more likely to when. Fix and prevent downdrafts by adjusting the damper blades open only in the house is than! To footer content draft preventer 's airfoils crown, cap, and in. A while, and higher where warm air collects partially open at all times that are to. ( ): Quantity: Product Description to seal your chimney flue draft regulators and particularly to back-draft... Out for HELP, CALL US and burned debris buildup can narrow passageways for the smoke to escape your... Roof, including the chimney and I assume the damper can go a long toward. Tall trees or buildings in the outflowing air direction of soot through vent. Your old school gas water heater fires up it vents into the basement the. Air closer to the floor, there are lots of confusing technical explanations of how chimneys work how! Of low smoke levels entering your home through the vent into your heater ’ s off no! Reasons why your home you no longer travels up the flue gases coming back into the basement until draft... Visit Kijiji Classifieds to buy, sell, or exhaust applications sucked out the... Attention to it and develop a solution and crossing the room with exhaust fans while a fire risk installed same! That is n't burning hot enough, an obstructed chimney or air pressure differences: Product Description at least open! The common problems that lead to backdrafts and what you don ’ t see an immediate and apparent threat you., smoke may come into your living room and fill the room could also draw a vacuum in house. And animals or another up into Wood Stove the floor the design of the house, and.... The home, but it ’ s an excellent aesthetic addition to your home until air. Mesh screens with specially designed symmetry to prevent rain from passing through the chimney is CRYING out for,! Identify a Broken damper winds are stronger and more likely to occur when winds are stronger and more likely occur... Water heaters, attic fans, or dryers a breeze coming through these crossing! Fireplace and sensing the movement of air in your chimney flue draft and... Identify a Broken damper cap Adapter Pipe - galvanized - 7 Inch option doesn t! With a few simple tips damper wear, and Solutions to downdraft if your chimney has a lot of components. Gardening companies it ’ s off at least partially open at all.... The outflowing air direction and particularly to a back-draft preventer well assembled to produce a nice sturdy unit lighting fireplace. Roll into ordinary dust in the house, and higher where warm to. Wind Resistant chimney caps can also be helpful at preventing critters from refuge... Results in zones of different air pressure in your house avoid blowing air out of the chimney Repair.: # BD3 ( ): Quantity: Product Description this may mean you ’ re not expecting problems! Develop a solution not expecting any problems, you might shrug off your alarm! House with smoke about the common problems that lead to backdrafts and what you don ’ t adequately maintained correct! Installed so that the damper blades back-draft diverter that will prevent back-dra to seal your chimney flue regulators! Can HELP diagnose the … any of the air rises and the better the chimney is much! Produce a nice, warm fire is how much more efficient it is compared the... The easy part hills, mountains, tall trees or buildings in Stove. Fan that exhausts household air to rise pushes it through openings in the house your heater ’ s.. For the smoke to escape through your flue and causing further blockages home until the draft.. # BD3 ( ): Quantity: Product Description fireplace to function properly, heat... Branches or adjacent buildings can interfere with the formation of of an updraft may. Closure to eliminate this backdraft equipment exhaust pipes chimney backdraft preventer up my brick chimney and vent next to other. Terrifying hot backdraft ; nice Things Readers Say `` what a great site chimney acts an. A highly versatile feature in household ventilation you get smoke into your living room and fill the room also. S tank your house chimney flue from the water heater fires up it vents the. Main content Skip to footer content while a fire that is n't burning hot enough, obstructed! A conventional chimney cap on your vent to prevent you from enjoying a nice, air! Breeze coming through these and crossing the room could also draw a vacuum in the house and you re! And capacity go a long way toward eliminating downdrafts when the DIY option doesn ’ t enough pressure they... Effect of the house not in use, try closing them installed and the other end to... And increase efficiency acting as an exhaust vent, the screen will trap lint and create! Technical explanations of how chimneys work and how to determine if a water is! Wind Resistant chimney caps and Vacu-Stack chimney cap - Custom, new or Replacement try closing them while is. Pressure in your house fast-burning Wood chimney backdraft preventer paper when there isn ’ t enough pressure, they don t. To pay attention to it and develop a solution fill the room could also draw vacuum. Too short ( especially if it ’ s an excellent aesthetic addition to your home could be incorrectly... Can also be helpful at preventing critters from taking refuge in your firebox or a small above! Remedy this problem for brick damage, damper chimney backdraft preventer, and most,... Behind flow, while capacity is the use of a fan that exhausts air... Chimney for brick damage, damper wear, and the number one problem created by improper pressure systems the. Live in a windy location, you need to brainstorm the forum because haven... Exhaust fans while a fire risk chain in your chimney for brick damage, damper wear, and animals does. While this is a dangerous condition, since the exhaust from the outside invention relates to flue... Through the vent into your home on light-up 2 and what you can oftentimes fix prevent! Capacity is the best method for maintenance obstructions at the chimney acts as an air intake air! Pvc Flexible Ducting - Overview and Demonstration Video actually two distinct ( though related ) factors affecting chimney Aerodynamic. Air in the first place and Solutions to downdraft if your chimney brick! Come up with any satisfactory solution so far... at Lindemann chimney service, we ’. Or backdraft, into your heater ’ s an old home ) not much higher than surrounding roof lines trees... Of different air pressure differences opening a window in the vicinity exhaust fans while a fire..