Passive Fire Protection

To better understand passive fire protection we need to firstly understand the concepts of “Compartmentalization” and “Flashover”.

Compartmentalization is the process of dividing large areas into smaller areas such as rooms within a level of a building. Each room may have a different function. You may have a plant room, an office space, a toilet area, and amenities area etc. In dividing large spaces into smaller areas we can then minimize the effects of one area on another area within the same space (e.g. two rooms on the one level of a building).

Flashover is the point at which there is the near simultaneous ignition of all combustible material in an enclosed area such as a room or the floor of a building (see the link at the end “Living Room Flashover). When certain materials are heated they release flammable gases. Flashover occurs when the majority of surfaces in a space are heated to the ignition temperature of the flammable gases. Flashover normally occurs at 500 °C (930 °F) for ordinary combustibles.[i]

If we look at a Time/Temperature curve[ii], you can see that for a fire to reach a temperature of 500 °C can take less than 10 minutes. From the “Living Room Flashover” video you can see that this occurs in the simulation in less than two minutes.

Passive fire protection measures ensure a building’s structure remains stable during fire, keep escape routes safe, limit the spread of fire, heat, and smoke from one compartment to another, so people have time to get out and fire officers have time to get in.[iii]

If we look at a room like a balloon, the objective of passive fire protection is to keep the air in the balloon for as long as possible. If we have a hole in the balloon the air escapes. If we have a hole in a compartment and there is a fire within the compartment, the fire can move from the compartment through the hole to an adjoining compartment and spread or alternatively the hole can provide additional oxygen to fuel the fire and accelerate the progression of the fire.

Plug up the holes, the obvious and the not so obvious

Passive fire protection is the process of “plugging up the holes”. For a room to be useful you have to be able to get in and out of it. For this to occur you have to create a hole in the wall into which you put a door so you can get into and out of the room.

Now we are in the room we need air so we run an air conditioning duct through the ceiling to the room. If we pump air into the room we have to allow air to leave the room so we leave a hole in the wall above the ceiling to allow the air to circulate through the room.

We want a drink so we go to the sink in the room and pour a glass of water. The pipes carrying the water and the waste from the sink go through the floor to the underside of the roof of the room below.

We plug our laptop into a power point. The cable for the power point runs through the wall and across the ceiling of a number of other rooms to the electrical distribution board.

So for our simple room we have a few holes which during normal activities are required to be there but in a fire can allow fire to spread quickly from one room to another if they are not adequately addressed;

  1. Doorway (Access and Egress Provisions)
  2. Air Conditioning Duct Work and Openings (Mechanical Services)
  3. Electrical Cabling through Walls and Ceilings (Electrical Services)
  4. Pipe Work through Floor Slabs (Hydraulic Services)

Passive fire protection is used to address these issues. The most obvious hole, the doorway, can be protected by the installation of a fire door with an automatic door closer so the door remains closed at all times and does not rely on people to close it.

The air condition supply ducts and return air ducts’/openings can be fitted with fire dampers which activate in a fire to close off the duct or opening and minimise the spread of fire and smoke. Fire dampers are not so obvious and are often installed incorrectly or not installed at all.

The walls can be fitted with fire resistant lining materials (such as fire rated wall sheeting) so a fire in the wall (possibly from electrical cabling) can be contained within the wall and not spread into the room. Fire rated pillows can also be installed in opening made through walls above the ceiling level to run cabling from one room to another.

Pipe work penetrating through the floor can be fitted with fire collars which act as a barrier around the pipe work to minimise the spread of fire through the floor into the ceiling of the room below.

The illustration below gives an idea about the various passive fire protection systems you may find in your facility.

Example of a fire and smoke compartment showing passive fire and smoke protection systems[iv]

 

 

Legend

  1. Fire and smoke barriers
  2. Structural fire-resistant elements–Beams, columns, trusses
  3. Fire-resistant doorsets
  4. Smoke doors
  5. Fire-resistant shutters
  6. Fire-resistant glazing
  7. Access panels and hatches
  8. Ducts and dampers
  9. Fire stopping of service penetration and control joints

Passive Fire Protection measures are intended to contain a fire in the fire compartment of origin, thus limiting the spread of fire and smoke for a limited period of time. This limited period of time is the time needed for people to safely evacuate the building. Fire protection is provided for life safety. Property and financial loss prevention is a by product of keeping people safe and having effective fire systems protecting our buildings.

Passive fire protection as with all fire protection systems and equipment should be installed, serviced and maintained regularly by trained, and where required, certified personnel.

To visualise the importance of passive fire protection the following photo[v] shows passive fire protection in action. The photo is an aerial photo of a brewery fire. You can clearly see how effective passive fire separation can be in protecting the lives of the people in the adjoining space and also the additional benefit of the protection of the structure of the adjoining space.

Looking for further information

The links below are provided purely for your convenience. They do not imply endorsement of or, association with any products, services, content, information or materials offered by or accessible to you at the target site.

http://www.pfpa.com.auPassive Fire Protection Alliance
http://www.nfpa.orgNational Fire Protection Association
http://irc.nrc-cnrc.gc.ca/Institute for Research in Construction/NRC
http://www.metacafe.com/watch/682670/from_living_room_to_inferno_in_under_2_minutes/-Living Room Flashover Video
http://www.firetactics.com/FLASHOVER.htmRapid Fire Progress & Flashover related fire development
http://afscc.org/Alliance for Fire & Smoke Containment & Control
http://www.eapfp.com/European Association for Passive Fire Protection
http://pfpf.org/Passive Fire Protection Federation (PFPF)
http://www.l-com.com/multimedia/video_clips/video.aspx?ID=13100Videos showing flammability of cables based on jacket rating
http://www.fpaa.com.auFire Protection Association of Australia
http://rfidams.wordpress.comPeter Mole’s Blog Page

References
[i] NFPA Fire Protection Handbook, 2-106
[iv] Australian Standard 1851-2005 Maintenance of Fire Protection Systems and Equipment (Page 163, Figure 17.1)
[v] Technical Guide TG-005 (Page 15), John Rakic
Disclaimer This article was written by Peter Mole General Manager at Taylors Doors and Frames and while every care has been taken in the compilation of this information and every attempt made to present up-to-date and accurate information, we cannot guarantee that inaccuracies will not occur. All copyright and trade marks accessible via the links in this article are owned by the respective website owners, or their licensors.

 

 

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