THE SCIENCE OF ACTIFAN

DOCUMENT A.

THE USE OF NEGATIVE PRESSURE DEVICES
IN FIRE SAFETY & VENTILATION OF BUILDINGS

POSITIVE PRESSURE ATTACK (PPA) FIRE FIGHTING

Buildings have a residual static pressure which can be influenced by the use of positive or negative pressure ventilation. For instance, 'the positive pressure mechanical ventilation system' draws in air from outside the building & raises the static air pressure within.   Posititive pressure fans are also deployed by the fire brigade to the same effect. The positive pressure increase forces acrid  smoke to escape from eleswhere in the building, an effect which can be controlled & assisted by installing  Actifan to upstairs windows.
 
 
Strategically positioned fans are often otherwise used to achieve positive or negative pressure ventilation in buildings, simply to maintain a healthy atmosphere inside.
 
Household extractor fans are an example. Actifan is a uniquely intelligent negative pressure extractor fan which utilises an opening window to extract noxious fumes by a wireless signal from smoke & gas alarms, or from a remote control.
 
When there is an indoor gas escape, Actifan will forcibly extract gas from the building.  The negative pressure will also cause fresh air to be drawn back into the building through any opening, big or small.
 
 
 
In a household fire, the products of combustion cause positive pressure in the building.   This can increase well beyond 7% when water is applied to extinguish the fire.   The fire brigade sometimes use a mobile fan/blower at the fire attack entrance, increasing positive pressure within the building still further.  However, the greater the positive pressure, the more important a means of exhaust from the building, without which smoke or fire may be forced to exhaust from the attack entrance putting firemen at  risk.
 
1. Actifan works to form an area of negative pressure which will draw smoke forward of the fire, ahead of advancing fire fighters & over the heads of trapped victims. By releiving excessive positive pressure it can assist the fire brigade.
 
2.  People are also sometimes trapped by fire  in an upstairs room where  survival depends on keeping the room free of acrid smoke.   With the door closed & preventing ingress of smoke from the fire below,  Actifan will rapidly extract fumes & circulate fresh air which may enter freely from another opening window, or the upper aperture of a centre pivoting roof window, for which Actifan Mk1  is designed.
 
Further details of the fire service's implementation of positive & negative pressure fire fighting techniques are to be found at the following link here