Hypoxic air technology for fire prevention

Hypoxic air technology for fire protection, also known as Oxygen Reduction System (ORS),is an active fire protection technology based on permanently reducing the oxygen concentration in a protected room.Unlike traditional fire suppression systems, which typically extinguish fires after they are detected, oxygen-hypoxic air is able to prevent fires.

Description 

In the volume protected by anoxic air, a hypoxic atmosphere at atmospheric pressure is continuously maintained:hypoxic means that the partial pressure of oxygen is lower than sea level, and atmospheric means that the atmospheric pressure is equal to the atmospheric pressure at sea level.Typically, 1/4 to 1/2 of the oxygen contained in air (i.e. 5% to 10% of air) is replaced by an equivalent amount of nitrogen: thus, a hypoxic atmosphere contains about 15 Vol% oxygen and produces 85 Vol% nitrogen.Ordinary materials cannot ignite or burn when exposed to localized, small-scale ignition sources in an oxygen-deficient atmosphere at atmospheric pressure.Reducing the oxygen level to 15% will not achieve the conditions under which the fire will not start or be extinguished. However, it reduces the likelihood of a fire by increasing the required ignition energy and there is also a sign of increased ignition time.

Design and operation

Air with reduced oxygen content is injected into the protected space to reduce the oxygen concentration until the desired oxygen concentration is achieved.Then, due to air infiltration, the oxygen concentration inside the protected volume rises: when it exceeds a certain threshold,hypoxic air is injected into the protected volume again until the desired oxygen concentration is reached.An oxygen sensor is installed in a protected space to continuously monitor the oxygen concentration.After careful evaluation of materials, configurations and hazards, the exact oxygen content to be kept within the protected volume is determined.The table lists ignition-limited oxygen thresholds for certain materials. Alternatively, the ignition limit threshold is determined by performing a suitable ignition test as described in BSI PAS 95:2011 Specification for fire protection systems with hypoxic air.Smoke detectors are installed in protected spaces because, similar to gas suppression systems, hypoxic air does not prevent smoldering and pyrolysis processes.

Air with a low concentration of oxygen is produced by a hypoxic air generator, also known as an air separation unit.There are three different types of hypoxic air generators: membrane-based, PSA-based, and VSA-based.VSA-based hypoxic air generators generally have lower energy consumption compared to PSA-based and membrane-based generators.Hypoxic air generators can be located inside or outside the protected room.Hypoxic air systems can be integrated with building management systems and can include systems for recovering heat generated by hypoxic air generators that would otherwise be wasted.Air with a low concentration of oxygen is delivered to the protected space through dedicated ducts or, more simply, through the existing ventilation system.In the latter case, no dedicated piping or plumbing is required.

Combined use of hypoxic air for fire prevention

Hypoxic air fire protection systems can also be used for purposes other than fire protection, such as:

• High altitude training

• Health 

• Protect artifacts and objects from degradation or oxidation

• Prevent food spoilage, commonly known as modified atmosphere packaging.

Combining fire protection, indoor climate and reducing artefacts/food degradation is a whole new approach to fire safety systems.

Application

The benefits of fire prevention rather than fire suppression make hypoxic air suitable for applications where fire would cause unacceptable damage. Unlike conventional fire suppression systems, no dedicated piping or nozzles are required.

Hypoxic air for fire protection is used for:

• Data center/ICT facilities

• Store high value items

• Archives

• Freezers and cold storage

• Large warehouse

• Paper mills

• Estate application

• Telecommunications

• Substation

• Utilities

• File storage

• High-bay warehouse

Reduction in artifact degradation and food spoilage benefits applications such as food warehousing,storage and archiving.

Effects on health

Under U.S. Code of Federal Regulations (OSHA), fire protection systems that result in oxygen levels below 19.5% are not permitted in occupied spaces if supplemental respirators are not provided to employees.However, some people believe that low-oxygen air is safe for most people to breathe.Medical research has been done on this topic.Angerer and Novak concluded that "working environments with oxygen concentrations as low as a minimum of 13% and normal air pressure do not pose a health hazard, provided that precautions are observed, including medical examination and limitation of exposure time."Küpper et al. Say oxygen concentrations between 17.0 and 14.8% do not pose any risk of hypoxia in healthy people.It also poses no risk to people with moderately severe chronic disease.The ability to work vigorously decreases with lower concentrations, while the duration of exercise that can be sustained becomes very low below these levels, below about 17%, and if one is going to spend more than 6 hours indoors, one may need to rest outside the environment , especially if any physical exertionPressurized aircraft cabins are typically maintained at 75 kPa, which is the pressure found at an altitude of 2,500 m (8,200 ft), resulting in a partial pressure of oxygen of approximately 16 kPa, which is the same as a 15% oxygen concentration in hypoxic air applications Sea level pressure.However, the passengers are sedentary and the crew has immediate access to supplemental oxygen.Hypoxic air is considered clean air, not polluted air, when assessing hypoxic hazards.

Information about entering protected areas (i.e. low-oxygen atmospheres) is stated:

• AI, Arbeitsinspektorat;

• SUVA, Schweizerische Unfallversicherungsanstalt;

• DGUV, Deutsche Gesetzliche Unfallversicherung;

• UIAA, Medical Committee of the International Mountaineering Association.