Oxygen Monitoring

DOE-STD-1066-99

15.3.1.2 Inerting System Design Guidelines

o The system should be designed and installed in accordance with the

applicable industry standards as supplemented by DOE criteria.

o When required or when used as a substitute for other required automatic

fire suppression systems, gloveboxes should be purged with an inert gas

(commonly argon or nitrogen). The level of inerting provided should be

sufficient to prevent ignition of the material(s) present. A safety factor

should be included in establishing the inert gas design concentration.

The safety factor compensates for errors in instrumentation or other

conditions which might lead to an increase in oxygen level. For

deflagration prevention, the flammable/combustible concentrations

should be maintained at or below 25 per cent of their lower flammable

limit. For combustible and pyrophoric metals, the oxygen concentration

should not exceed 25 per cent of the level required for combustion.

(Note that some combustible metals (e.g., aluminum powder) will burn in

atmospheres other than air. Thus it is important for the designer to

select an appropriate inert gas and establish a design concentration

based upon the hazard.)

15.3.1.3 Oxygen Monitoring

Where inert gas purging systems are installed, oxygen monitors should be

provided to ensure the necessary concentration of inert gas is maintained.

If an alarm (excess oxygen) condition is reached in the glovebox, the oxygen

monitoring system should:

o shut down the operations and electrical power to the glovebox, when

warranted by the FHA, provided this action does not create an additional

hazard; and

o activate a local audible alarm (as a minimum) and, if high noise levels or

other conditions warrant, cause a local visual alarm to be activated.

The designer and fire protection engineer should also evaluate gloveboxes

equipped with inert gas purging systems to determine if:

o an emergency purge or pressure relief system should be installed; and

o the hazard justifies providing annunciation at a continuously staffed

location.

NOTE: The designer must analyze the consequences of curtailing

operations after an oxygen alarm and establish the procedure necessary to

shut down and stabilize conditions in the glovebox following an alarm.