by 1. G. Rimen Research Report Number 81 ",-P ~ Home Office BUILDING A SAFE, JUST AND TOLERANT SOCIET Y Central Fire Brigades Advisory Council Scottish Central Fire Brigades Advisory Council The Use of Positive Pressure Ventilation in Firefighting Operations By 1. G. Rimen The text of this publication may not be reproduced, nor may talks or lectures based on material contained within the document be given, without the written consent of the Head of the Home Office Fire Research and Development Group. Research Report Number 81 2000 © Crown Copyright ISBN 1-84082-487-5 ~ ~ Home Office BUILDING A SAFE. JUST AND TOLERANT SOCIETY The Use of Positive Pressure Ventilation in Firefighting Operations This report describes the conclusions of a programme of work on Positive Pressure Ventilation (PPV) undertaken by the Home Office Fire Experimental Unit. Following a survey of what was known about the tactic, a number of scenarios were investigated to try to identify any lessons which could be learnt which would be of use to the fire service. This report also seeks to combine the conclusions of the various studies to derive more general conclusions. and firefighting techniques, to see whether the overall INTRODUCTION cost of such fires could be reduced. The Fire Research and Development Group presented the Ventilation is the removal of heated air, smoke and results of this study to the JCFBO in October 1992, other airborne contaminants from a structure, and and the committee concluded that there were three their replacement with fresher air. Tactical areas where further research should be requested. ventilation of a fire requires the intervention of the fire service to open up the building, releasing the These were: products of combustion and allowing fresher air to enter. Positive Pressure Ventilation (PPV) is • To extend scientific understanding of extinction achieved by forcing air into a building using a fan, to processes; increase the pressure inside, relative to atmospheric • To identify whether damage control could reduce pressure. the cost of large fires; • To review the applicability of ventilation at large The term 'offensive ventilation' is sometimes used to fires . describe the circumstances when ventilation takes place close to the fire to have a direct effect on the The Home Office Fire Experimental Unit (FEU) fire itself, to limit fire spread, and to make conditions safer for firefighters and anyone else within the commissioned Warrington Fire Research to undertake building. The term 'defensive ventilation' is a survey of what was known about ventilation, and sometimes used to describe where ventilation is used their report was received in mid 1994, and published away from the fire, to have an effect on the hot gases as FROG Report 6/94. Amongst other conclusions, and smoke, particularly to improve access and escape this study also identified a firefighting tactic, being routes and to control smoke movement to areas of the developed in the USA, which might be of benefit to building not involved in the fire . the United Kingdom fire service - Positive Pressure Ventilation (PPV). This makes use of portable fans to accelerate the effects of tactical ventilation. Even THE HOME OFFICE'S LARGE FIRE though their effectiveness was limited by their size, PRO.JECT there were a number of circumstances, not covered by the large fires project, where they could prove useful. In 1991, the Central Fire Brigades Advisory Council's Joint Committee on Fire Brigade The JCFBO endorsed a proposal to initiate a further Operations (JCFBO) requested a pilot study into the research project into the possibility of using PPV in fighting of large fires, covering firefighting agents the United Kingdom, and work started in early 1995. THE USE OF PPV IN USA AND had led to an increase in backdraught incidents. Far EUROPE from increasing the potential for flashover, US firefighters have learnt that tactical ventilation reduces the number of flashovers. Introduction PPY generally received most application at fires in As a first step, the FEU decided to implement a residential properties and small commercial second recommendation of the initial study - that fire buildings. The timber construction of most single officers from the UK meet their counterparts in the family dwellings lends itself to rapid fire involvement USA and other European countries to discuss PPY and this may explain the US tendency toward early tactics. The work is reported in FRDG Report 8/96. ventilation. However, the fact that PPY is used so prolifically tends to dispel the concern that it The study team comprised an independent consultant promotes rapid fire spread. and four Station Officers, with recent operational experience in the use of PPY. The brigades Opinion was mixed over the benefits of PPY in large represented varied in size, the nature of risks covered volume commercial or industrial buildings. Some and their exposure to PPY. It was hoped that this claimed that PPY can assist fire attack with multiple would provide for a good balance of opinion. fan arrangements, others claimed that the tactic is only suitable for damping down and clean-up operations. Positive Pressure Ventilation in The USA PPY is not used by all fire depa11ments in the USA. Positive Pressure Ventilation in Europe Even within the departments visited, which do promote the tactic, PPY is not universally accepted. Prior to the introduction of PPY, ventilation practices The majority of fire officers do, however, use PPY. in the departments visited were very similar to those in the UK: ventilation was only used for smoke US experience suggested that the two factors most clearance after control or extinguishment of the fire. likely to cause a problem during fire attack were: Despite an initially sceptical response PPY is now • not having water readily available, or commonly used in the majority of fire departments in • not creating an exhaust vent before using the fan . Germany. PPY is only used by a minority of departments in Holland. The firefighters questioned could only recall two or three incidents where PPY had intensified a problem Problems have been experienced during the use of and caused greater damage. None could quote a PPY, the most common of which are: situation in which the misapplication of PPY had led to a loss of life. Experience suggested that problems • making openings in the wrong place; arose through misapplication of the tactic, not as a • making too many openings and reducing the result of any inherent danger in employing PPY . efficiency; • failing to manage the airflow route. PPY will introduce oxygen to the fire and a substantial increase in localised flaming is common. As in the UK, most dwellings in Europe are of This does not normally present a problem because masonry and tile construction which makes it difficult operating procedures demand that a fire attack team to create openings in the roof and walls. The German with charged hoselines should be in position before fire officers believed that PPY is well suited to fans are used to ventilate the structure. horizontal ventilation in European type construction. During overhaul (i .e. damping down) or salvage, PPY The need to co-ordinate the activities of the fire attack can intensify smouldering or spot fires. This is and ventilation crews by maintaining communication perceived by many to be a distinct advantage as it was stressed as paramount. reduces the chances of missing a problem which could result in a recall. There was no evidence to suggest that the use of fans 2 The Application of Positive Pressure Ventilation in .. the lead set by fire The United Kingdom US and taken up some the key to success lies in In the team considered that the concept and programme of behind the technique of PPY was relatively easy to allowing time for review and understand and the equipment The and skills to apply the would not be as simple to .. Before implementing PPY it would be necessary for all personnel to have a full knowledge of the of fire behaviour and the team that PPY could be used influence of ventilation on fire in the United in a number of areas. should be carefully matched of the tac tic. It .. The use of PPY would be to would be to train personnel in the use of PPY fire attack until they have operations. mastered the basics of using the tactic after fire control. of fire deaths and injuries, both for and members of the public, occur in family dwellings. PPY was considered to RESEARCH UNDERTAKEN THE be particularly suited to these types of .. The use of pre-installed systems to both to protect means of escape and The Use ofPPV in Cellars assist access, is recognised as a benefit in tall buildings. PPY provides the fire FRDG 6/95 describes a series of trials service with an opportunity to achieve similar designed to assess the effectiveness of removable or results in where these breakable pavement or stallboards, in the event provided, e.g. Iow-rise of a basement fire. Fires in basements are notoriously and commercial difficult for brigades to combat because, need to descend from the above .. The benefits of PPY in volume structures, into the basement through a of hot gases to carry e.g. commercial or industrial are open out search and rescue or The to question. However, the tactic is to be of opportunity was taken to include the use of PPY in use in removing smoke after the fire has been this work. controlled. In these use was made of the cellar in the The study team felt that the reported hazards Industrial "B" building on the Fire Service associated with the use of PPY were less serious than fireground Figure 1), which had a removable believed: pavement installed by FEU for the purpose.