Back Draft:

This was a new word for us. In the fire service it means one thing, but while dealing with building owners in New York City they used back draft in another sense. You probably refer to it as updraft, the stack effect, or the chimney effect. So what you know as the ignition of carbon monoxide in a structure or void, building owners were calling the air rushing up the chute 'back draft'.

This occurs when a temperature differential exists between the interior and exterior of an enclosure. These differentials are present at all Arial in vertical shafts such as elevators, garbage chutes and stairwells in any high-rise building and cause air to move up through the various shafts and dramatically impacts on the interior building envelope. The venturi effect can further compound Back Draft depending on the building's height, location and the surrounding landscape.

When you want to heat or cool something a common method is to run a pipe and put something in that pipe to either heat or cool the area around it. The same thing happens with a trash or linen chute. The air rushing up the chute can cause the area around the chute to either heat or cool, depending on the season and temperatures. There are also cracks and openings where the chute intake doors are installed on the floor levels, which can allow air to move in either direction.

Back Draft's presence in any high-rise building is indicated by:

• Air blast when accessing the chute on upper floors
• Odour and stench contaminant traveling up the chute onto floor spaces
• Elevator doors are hard to close
• Whistling wind noises through the building's lower levels and lobby
• Roof top garbage chute outlet cages being full of debris
• Cooler or warmer temperatures throughout the building