Fire prevention and occupational safety

Barry Bell looks at the role of hypoxia work in active fire prevention and the implications for occupational safety.

“The required extinguishing concentration is then maintained for at least 30 minutes”

Although fire prevention technology is already widely accepted in European countries, it is still relatively new in the Middle East region, if not still unknown in some parts. The interest in the application of fire prevention is however gaining impetus here, clearly recognisable by the huge amount of emails I receive from companies with assets that they feel need protecting and engineering practitioners that wish to apply the technology in their projects. One of the most recurring questions I have received relates to the impact of fire prevention systems, or reduced oxygen concentration levels, on the human being.

First of all, I will explain the basic concept of fire prevention for the benefit of those who may not know what we are talking about. Traditionally, high value assets whether they be mission critical IT/communication equipment, state archives housing irreplaceable documents or artifacts or high volume chemical storage facilities, where water based fire suppression systems were deemed undesirable, gaseous fire suppression systems were employed.

The common denominator for the function of inert gaseous suppression systems is firstly, the reliable detection of a fire, followed by an electro-mechanical activation of the suppression system followed by a rapid oxygen depletion within the targeted space. Oxygen levels in the targeted space are typically reduced to between 11-1,5Vol percent within 30 to 60 seconds. The required extinguishing concentration is then maintained for at least 30 minutes. The design standards for gaseous fire suppression systems impose strict life safety measures to protect human beings from harm.

In comparison, a fire prevention system would be designed to permanently reduce oxygen levels within a target space to a volume concentration whereby combustion of the materials cannot take place. The oxygen concentration levels vary according to the materials being protected. For the majority of class A combustibles, levels between 14 and 15Vol percent are sufficient to prevent a fire.

The common denominator for the function of a fire prevention system is the utilisation of the natural air, whereby the air is passed through a molecular diffuser, separating the oxygen and nitrogen content. While the oxygen content is discarded, the nitrogen is guided into the target space, diluting the air within the space and thus reducing the oxygen concentration to the desired level.

The oxygen level within the target space is monitored by multiple oxygen sensors that communicate their measurements to a control panel, which in turn regulates the production of nitrogen. In this manner, the desired oxygen level can be maintained permanently within the target space.

So the question is, "How does this affect human beings that enter a space protected by a fire prevention system?" To answer this question, we need to understand a little more about hypoxia, a condition whereby a deficiency in oxygen supply to the body's tissues/cells occurs.

Apart from 'classical' hypoxia, which is almost an exclusive problem for mountaineers and, to a lesser extent, for air-travelling business men, hypoxia is also used for altitude training and a variety of sports training as well as many other purposes. As a consequence more and more people are being exposed to hypoxia.

Although there are some minor physiological differences between simulated (iso-baric) and real altitude (hypobaric hypoxia), these are not relevant for occupational health and safety. Therefore the term altitude in this article includes the situation of simulated altitude (achieved by isobaric hypoxia) or equivalent altitude (a term, which is often used for aircraft cabin pressure).

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If you would like to read more, visit the MENA Infrastructure website to see the extended version here.

Barry Bell is the Managing Director of Wagner Fire Safety Management Consultants, Middle East, and a licensed Fire Engineering Consultant in the United Arab Emirates.