Smoke and fire mode air handling controls

October 7, 2014

Smoke kills before flames ever penetrate the boundaries of a room. Toxic fumes block breathing and burn the eyes, stopping panicked groups and individuals from seeing a logical escape route. Mitigating the presence of smoke and poisonous fumes, even for a matter of minutes, could mean the difference between life and death. Lateral thinking indicates the need to combat the conflagration on a separate front, and inter-system cooperation is key in accomplishing this goal. The system in question is the HVAC ducts and vents that proliferate most medium to large buildings. They generate cool air and circulate that air to prevent a stale environment. They temperature-control hot spaces, warming rooms when they're uncomfortably cool, but the air handling unit that drives the air into each space also holds the power to starve a fire.

Close down the fans and dampers within an air conditioning system and a fire is instantly cut off from the oxygen it needs to grow. That's a huge plus when fighting to save lives. Also, the opposite would be true, a still functioning fan and damper would feed air into the heart of the fire, so a fire alarm system coupled to the environmental controls must void this source, halting motors and mechanical louvers when the alarm is activated. This first stage reaction is an automatic safeguard designed to initiate as soon as a fire alarm is triggered. Typically, this passive operation model is supported by an active extension to the controls in the form of an incorporated manual control sub-system. These keyed points of access are only available to fire fighter and building managers. They allow a permitted individual holding the requisite key to maneuver dampers and fans. The concept adopted here is the manipulation of pressure density within different zones of the afflicted structure. Instead of leaving fans in the closed position and dampers sealed, a fire fighter can actively void smoke and redirect its natural flow by creating air pressure differentials. The strategy works in tandem with standard fire and smoke suppression techniques, removing air or using that air to force smoke away from an occupied zone.

While not foolproof, window breakage will negatively impact the differential, damper and air handler manipulation saves lives, clearing smoke so that survivors can see a safe path from a room before the flames reach a deadly height. Advanced operation typically adds extra pressurization to key areas of a building, to emergency stairwells and designated fire escape routes. This important provision targets a safe conduit, keeping the pressure differential in the stairwell and the escape corridor. Smoke will be kept at bay to allow fire fighters to make their way to the core of the flames and the occupants to make a hasty retreat. The two-tier strategy is simply an extension of current building engineering, the application of environmental controls in stopping oxygen from reaching the fire. The second punch, the delivery of a pressurized zone of clear air is the active part of the twin dynamic.

Connor Pincus Group. Consulting Engineers.

Address: 1196 Toorak Road, CAMBERWELL, VIC 3124

Phone: (03) 9835 5000
Fax: (03) 9835 5050

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