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Fire detection in warehouses

With the new release of SANS 10139, there have been multiple changes that impact on how one would protect a warehouse or large facility.

Ensuring high levels of fire safety in warehouses, particularly in the growth of the unmanned warehouse sector, where there is a reliance on automatic fire detection systems being able to identify a real fire and notify emergency services as quickly as possible. As more consumer retail moves online and bigger and more remote distribution hubs are being built to supply this demand, there’s a real challenge when it comes to installing fire detection that can cover these large open spaces and protect their valuable contents.

While traditional point detectors are the most suitable option for many applications, there are other options available:

1. Beams.

2. Aspiration detectors.

3. Video-based fire detection.

All of these devices would, in the right application, offer a good solution to cover a wide area, such as the open spaces found in most ‘super-warehouses’ where a complex network of multiple overlapping sensors must be configured in order to achieve the required coverage. And this doesn’t take into consideration the height of the ceilings in these huge spaces, which in most instances, negates the acceptable use of point detection.

Below is a detailed analysis of each device type.

Beam: Optical beam smoke detectors are increasingly considered the most appropriate option for providing wide-area detection in these types of environments, as each one can cover an area that would normally require up to 15 point detectors.

As a beam detector works by responding to the attenuation of light between two points, anything that partially obscures the beam is potentially a trigger for an unwanted alarm. However, in most modern systems this problem has been eliminated thanks to time-based algorithms that distinguish between unwanted obscuration and genuine fire conditions.

Point detector: Multisensory devices can detect heat, smoke or other gases, however, they are not always the best option depending on site layout and requirements.

Aspiration system devices: These types of devices have been around for a long time and detect smoke with a small sensing hole in a piping system running along the entire warehouse or area being covered.

Video-based fire detection: This product has been around for some time and is fast gaining momentum, it has recently been added to South Africa National Standard and allows for the early detection of both smoke and fire as well as giving the would-be respondent the availability to see what the cause of the fire is and what to expect when they respond.

The siting and spacing of beam detectors is an important consideration. Reference should be made to national or local codes such as the recommendations found in the Fire and Life Safety Code of Practice, SANS 10139, NFPA 72 and the UK’s BS 5839, the last of which specifies the general height limit for point type smoke detectors. It is also necessary to ascertain the height of the heat barrier in a building as a detector that is positioned above this level could fail to operate effectively because of thermal interference, resulting in a delayed response to a genuine fire. Again, guidance is available on how the heat layer can be worked out and in new builds this is often completed by the architect or consulting engineer.

The fundamental criteria to address when selecting a detection technology for any location are appropriateness of location, choice of detection coverage and ease of installation and maintenance.

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