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

protective measures.

Keywords:  Fire  protection,  fire  prevention,  oxygen  reduction,  hypoxic

air, standardization


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 [1]. 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

safety requirements




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 [4]. 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  [۴]  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   [۵].   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.