KEDS –S300 HYPOXIC AIR FIRE SUPPRESSIONS SYSTEM
The technology of fire protection using a oxygen-reduced atmosphere
to prevent fire from starting or propagating is quite new in comparison to
a sprinkler system or even a gas extinguishing technique. This paper
recalls the history of the development of new standards and regulations
to cover this technology of oxygen-reduced atmospheres which started
in Europe and has now, by demand from owners, reached North
This paper gives an overview about the design and installation
guidelines available today all over the world, it also explains the main
requirements and analyses the slight differences.
Regarding health and safety regulations the paper emphasizes the
different positions of OSHA and the European insurances. It introduces
the concept of risk classification corresponding to different operating
ranges of oxygen concentrations and describes recommended
Keywords: Fire protection, fire prevention, oxygen reduction, hypoxic
Fire protection using the oxygen reduction principle is an established
technology, installed and in operation in more than ۱۰۰۰ projects and
for more than ۱۸ years, mainly in automated warehouses and server
facilities all over the world. Peter Clauss has given an in-depth overview
at SUPDET in 2014 . The idea behind it is quite simple: reducing the
oxygen concentration in a room will prevent fire from starting or
propagating. However, oxygen reduction is achieved by complex
technical systems that are providing a flux of nitrogen or nitrogen-
enriched air into the protected areas [2
Even after many years of experience many questions arise all over the
place. Designers wonder how to determine the appropriate operating
oxygen concentration level and the required nitrogen-enriched air
volume flow inside the protected area. Manufacturers of oxygen
reduction systems ask certification bodies how to get an approval.
Certification authorities ask for standards that apply – either locally or
globally. Owners of facilities inquire about the measures to allow access
of people to protected rooms.
All this demonstrates the need for a full set of regulations and standards
to cover design and installation as well as health and safety issues of
oxygen reduction systems for fire protection in any part of the world.
Approval in the time before publication of any guideline
The Wagner Group company presented its first oxygen reduction
system for fire prevention under the OxyReduct ® trademark in 1998 on
exhibitions and conferences in Germany (Security in Essen, Wagner
Symposium) and started the operation of the first OxyReduct ® fire
prevention system in a server room in 1999.
How to get an approval for this brand new fire protection technique?
At that time, of course, no standard or guideline was available. For
cases like this, the German VdS referred to a specific procedure for the
approval of new extinguishing techniques described in document
VdS 2562. This includes tests of the extinguishing effectiveness as well
as reliability tests of the components. Wagner went through this
procedure and got its first approval from VdS in 2004. The experience
gained from these test series was helpful to write the planning and
installation guideline VdS 3527, first published in 2007
Another milestone was the first industrial installation in the US for the
protection of the world’s largest freezer warehouse in 2015, located in
Richland, Washington State bringing oxygen reduction on an industrial
scale to the US – although no local standard is on place. It has a
capacity of 115.000 pallet stalls and a volume of approx. 1 Million m³ /
۳۸ Million ft³. And now just north of the US border, Canada has its first
installation at Dr. Oetker’s new facility in London, Ontario.
Design and installation guidelines from VdS and EN to ISO and UL
Based on the VdS guideline from 2007 oxygen reduction made its way
through Germany and got into other European countries (and beyond)
within the last ۱۰ years. Consequently, a European standard was to
follow the German VdS guideline and today the prEN16750 is made the
platform for international designs and for the New Work Item Proposal
issued in September ۲۰۱۶ at ISO. The working Group ISO/TC
۲۱/SC 8/WG 9 just started its work to develop an international draft
standard on oxygen reduction systems .
Table 1 shows in chronological order how many national standards or
technical guidelines about design, planning, installations and
maintenance are now available to address relevant performance and
In countries without their own national guideline, especially in the
Middle East or in the Asia Pacific region, either European or US
guidelines are usually used.
The aim of the guidelines is to define rules for designing an effective
installation that safely maintain the appropriate operating oxygen
concentration even in case of a failure. They contain construction
requirements for the generators, the pipe work, the control equipment
and its power supply
A key issue is to determine the operating oxygen concentration.
Therefore, the guidelines include a list of known ignition threshold (e.g.
۱۵٫۹ or 16.0 % O 2 for plastic material like ABS, PVC, PP, PE) as well as
methods to ascertain ignition thresholds of unfamiliar materials. A safety
margin (۰٫۵ – ۱٫۰ % O 2 ) and tolerances in the oxygen measurement
have to be taken into account to calculate the operating concentration.
The safety margin is arbitrary and varies between the different
TRVB ۰٫۵ % O 2
SN ۰٫۵ % O 2 (with a fire alarm system or a sprinkler)
EN ۰٫۷۵ % O 2
Kiwa, SN, VdS ۱٫۰ % O 2
Fig. 1. Example of safety margins between ignition threshold and
maximum operating concentration.
EN and VdS require a minimum number of oxygen sensors in each
protected area to monitor and control the oxygen concentration. At least
three oxygen sensors are required, even for small areas. The amount of
sensors required depends on the volume of the protected area, as
shown in Table 2
If the oxygen concentration cannot be maintained within the control
range, the control equipment shall signal this abnormal condition. For
example, if a door to a protected room is left open for long time the
oxygen level may increase far above the control range even if the
generator don’t stop producing oxygen reduced air. In this case, a fault
shall be signalled (O 2 too high) to indicate a reduced fire protection. If it
happens that the oxygen level falls far below the control range then a
fault (O 2 too high) or even an evacuation alarm shall be signalled.
Figure ۲ illustrates the monitoring of the oxygen concentration with
upper and lower thresholds above and below the control range for the
example of an operating concentration in the range between ۱۵٫۰ %
and 15.2 % O 2 . The fault thresholds are thereby displayed in yellow and
the alarm threshold for evacuation in red
UL has published the outline of investigation UL 67377 which refers to
prEN 16750:2014 for the general design, installation and maintenance
of the system. UL mentions especially prEN 16750 regarding the upper
and lower thresholds to control the oxygen concentration. However,
UL 67377 includes references to UL standards, e.g. UL 429 for valves
or UL 508 for control equipment. In addition, UL 67377 introduces
requirements on functional safety according to IEC 61508 series to the
programmable logic controllers.
EN 16750 includes an annex on health and safety only for information
and refers to national regulations for working in areas with lower oxygen
Health and safety regulations: OSHA versus European Insurances
Being in an oxygen-reduced atmosphere is comparable to being at a
high altitude. The significant physiological factor is the oxygen partial
pressure. From an occupational health perspective, real altitude
(hypobaric hypoxia) and oxygen reduction (normobaric hypoxia) ar
considered comparable . For example, going skiing at an altitude of
۳۰۰۰ m (۹۰۰۰ft) in the Rocky Mountains is comparable to an oxygen
concentration of 14.3 % in an oxygen reduced protected area
In the US, the Occupational Safety and Health Administration (OSHA)
recognizes that, at higher altitudes, oxygen in air has a partial pressure
that is less than the partial pressure of oxygen in air at sea level;
accordingly, the Respiratory Protection Standard makes allowances for
employees who work at altitude. However, OSHA made these
allowances based on record evidence showing that such employees
usually are acclimated to the reduced oxygen partial pressures.
However, OSHA still considers any atmosphere with an oxygen level
below ۱۹٫۵ % to be oxygen-deficient and dangerous to life or health.
This is the reason why paragraphs (d)(2)(i)(A) and (d)(2)(i)(B) of the
Respiratory Protection Standard require employers working under
oxygen-deficient conditions to provide their employees with a self-
contained breathing apparatus or an equivalent equipment.
On the other side, the Institute and Outpatient Clinic for Occupational
and Environmental Medicine at the University in Munich  and the
Medical Commission of the Union Internationale des Associations
d’Alpinisme (UIAA MedCom) give recommendations on how to provide
health and safety for employees in different kinds of low oxygen
atmospheres . European National Accident Insurances have
compiled these recommendations for owners of facilities protected with
oxygen-reduction systems in specific health and safety publications, as
listed in Table ۳٫ These European publications apply to working in
environments with a reduced oxygen concentration down to ۱۳٫۰ %
without requiring any self-contained breathing apparatus.
Table 3. Overview of European health and safety publications
As a measure of precaution, no permanent work place should be
located in oxygen-reduced areas and uninterrupted exposure should
not last more than several hours. The above-mentioned publications
therefore define risk classes and corresponding safety measures, as
summarized in Table 4
The occupational health examination / screening of personnel focusses
on cardiovascular and pulmonary afflictions. It starts with a simple
questionnaire to determine heart and lung conditions
In addition, technical and organization measures such as access control
and signs indicating the oxygen-reduced atmosphere are recommended
to protect the personnel. The access shall be restricted to authorized
and instructed personnel. An audible alarm shall sound if the alarm
threshold is reached to initiate the evacuation of the oxygen-reduced
area. The Swiss SUVA requires a minimum safety level (SIL) of ۳ for
the safety functions of the measuring and control equipment.
First products standards
In analogy to conventional fire extinguishing systems where standards
like the EN 12094 series define the requirements and test procedures
for each system component, products standards are now available in
Austria and Germany for the key components of an oxygen reduction
system, as shown in Table 5.
Table 5. Products standards in Austria and Germany
Summary and outlook on future development
The required set of national and international standards and guidelines
on oxygen reduction system for fire prevention, which guarantee a good
quality level for performance and safety all over the world, has reached
a respectable level of maturity even if some more work is still pending,
especially at international level. The new ISO working group is facing
the challenge to find an international consensus between European and
US positions on designing and operating oxygen reduction systems.