Oxygen Reduction Systems: Removing the Threat of Fire in Warehouses
02.05.2013
It is widely acknowledged, “Prevention is Better Than Cure”. All traditional forms of fire
protection and extinguishing rely on a fire starting for them to work, meaning damage
and disruption is inevitable. In warehouses conventional fire protection is difficult to
install and maintain. Where business continuity and stock protection is paramount a
different approach is required – Fire Prevention.
In this article Lee James, OxyReduct® Sales Manager for WAGNER UK, details how Oxygen
Reduction Systems prevent a fire from occurring in the first place.
These days goods must be available around the clock - normally just in time. Modern high rack
storage areas in large centralised logistics operations are often at the heart of the solution.
However, having the focus on a single logistics site also increases the risk of a complete
system stoppage through the entire supply chain in the event of a fire. In warehouses where
goods worth millions are stored, even small fires can cause enormous problems.
Large open spaces such as warehouses and logistics’ facilities represent one of the most
demanding environments for fire protection designers. Requirements in the logistics sector
continue to grow - and with them the height and capacity of the rack storage areas. Smoke,
soot and water from sprinklers or firefighters can have devastating consequences, which is
why even small smouldering fires can cause immense damage.
Mini-load containers are very
practical, but also a fire risk. The
plastic containers burn comparatively
easily and melt quickly, allowing fire
to spread by means of the falling,
Fires that originate in the stock itself are rare. Most fires in logistics’ operations are caused by burning plastic drops.
defects in electrical equipment; present in almost all warehouses. This includes switch
cabinets and control boxes, electrical motors and, in deep freeze storage areas, refrigerators
and defrosters. Welding work used for repairs and maintenance also increases the risk of fire
immensely.
Ideal Fire Conditions
High rack storage areas reach heights of over 40 metres. This, together with the small gaps left
between the stored goods, provides ideal conditions for a fire to spread. Goods in higher racks
can become heated so quickly by the rising fumes that the flames suddenly spread right up to
the roof of the warehouse. This process can take only a few minutes if adequate protection is
not in place. Even slight exposure to soot or smoke can contaminate the stored goods and
render them unusable.
Oxygen Reduction Systems
For a fire to occur the three elements illustrated in Fig. 1 need to be in place; the removal of
one or more of these elements will cause the fire to be extinguished.
High rack storage areas provide ideal
Removing oxygen to prevent a fire from developing is not new. Gas suppression systems in
conditions for a fire to spread.
server rooms and the use of foam on flammable liquid fires both use the principle of
smothering the fuel to prevent fire development by removing the oxygen supply. However, for
both these systems to operate a fire would have been ignited and will have caused damage
before the process of extinguishing begins.
Oxygen Reduction Systems employ innovative technology that continuously reduces the
oxygen level in a room by adding nitrogen to the air. The oxygen is reduced to a level in which
most combustibles do not inflame and an open fire is impossible.
As well as creating a totally fire free environment for an area, Oxygen Reduction Systems do
not prevent the area being used by people. The effects of lowered oxygen levels on the human
body have been highly researched over the years and safety guidelines have been established
that allow staff to enter or work in the protected area.
Detecting fires as early as possible is one thing - extinguishing them is another. Installation of Fig. 1 – Triangle of Combustion
sprinkler systems involves the fitting and ongoing maintenance of extensive pipework
throughout the facility. This is often very expensive for large warehouses, combined with the
potential for water based extinguishing systems themselves to cause damage and disruption
when activated. The ultimate form of fire protection is therefore Fire Prevention to stop the fire
from starting in the first place!
Atmospheric Environment
The natural ratio of oxygen to nitrogen (see Fig 2.) remains the same at high altitude levels as
it does at sea level; the amount of oxygen is less because of the overall lower air pressure. The
amount of breathable oxygen in a fire-free environment is similar to the amount of oxygen we
would breathe in an aircraft cabin or up a mountain. But importantly the air pressure remains
Fig. 2 - Makeup of the Earth’s
the same as the ambient level.
atmosphere; which remains at these
Nitrogen is used to inert the area as it is completely non-toxic in any quantity and is easily
produced on site. Other benefits of Nitrogen are that it is electrically non-conductive and will
not harm any product stored in the area. The Nitrogen being fed into the risk area is in fact
fresh air with a 95 % Nitrogen content. This prevents the air within the risk area from becoming
stale and also prevents a build-up of carbon dioxide.
The Nitrogen is not stored in pressurised bottles, but produced as required by the Oxygen
Reduction System to replace natural leakage in the risk area. This allows accurate control of
the atmosphere within the risk and saves space. The equipment footprint for Oxygen
Reduction Systems is typically much less than comparable extinguishing systems.
Cold Storage Areas
The operation of conventional fire protection systems can be adversely affected in deep freeze
storage areas. Despite a temperature of -26 °C, there is a pronounced fire risk in these areas
because of the extremely dry air. At the same time, fire detection and fire extinguishing prove
problematic. Condensing humidity and the minus temperatures adversely affect the function of
conventional smoke detectors, which typically only operate down to around -20 °C.
Extinguishing fires with fire-fighting water containing antifreeze contaminates the goods in food
warehouses.
Inside high warehouses with such low temperatures heat only rises very slowly in the first
phase of a fire because of the low thermal lift. As a result of this, conventional fire extinguishing
systems often are not activated before the fire has already taken hold.
Oxygen Reduction technology and appropriate Aspirating Smoke Detection equipment is not
affected by any of these conditions or problems.
Field Proven Applications
Oxygen Reduction Systems are now field proven in a number of applications ranging from
small IT rooms, museums and archives, through to warehouses of 600,000 m³ and more. For
example, WAGNER’s OxyReduct® system has been adopted by over 600 organisations
worldwide.
Zurück zur Übersicht
© 2017 WAGNER Group GmbH
Visit Us
Fig. 2 - Makeup of the Earth’s
atmosphere; which remains at these
concentrations even at the top of a
mountain.