A non-magnetic CO2 sensor...


[13/05/15] In typical pioneering style Analox recently completed a highly specialised research project on behalf of a major military supplier.

The goal was to develop a carbon dioxide (CO2) sensor with an extremely low magnetic signature - a technology currently unavailable in off-the-shelf products. The initial results were promising and the resulting prototype fulfilled the required specification.

The availability of such a sensor would enable the production of gas-detection systems with a magnetic signature not larger than 5nT (nano Tesla), the limit specified by the NATO Standardization Agreement STANAG 2897 Class A. Compliance with this standard is becoming an operational necessity for defence applications which deal with magnetically sensitive ordnance.

The focus of Analox’s commissioned research was the feasibility of a non-magnetic CO2 sensor for use in re-breathers. A re-breather is a type of self-contained breathing apparatus designed to permit ‘recycling’ of exhaled air, by removing excess carbon dioxide and gradually replacing the depleted oxygen.

Re-breathers incorporate both an oxygen tank and a canister of soda lime which absorbs, or ‘scrubs’ the carbon dioxide from the exhaled air. This canister must be physically repacked with absorbent material before use but the process has been known to fail. Any deficiencies in either the packing process or the quality of the absorbent may result in potentially fatal CO2 poisoning, known as hypercapnia.

The dangers of hypercapnia are well-documented. Consequently strict procedures exist wherever divers or emergency personnel are responsible for checking and repacking soda lime canisters for re-breathers. Nevertheless the physical nature of the task remains vulnerable to poor maintenance or human error.

Safety is greatly enhanced by the integration of a CO2 sensor in the re-breather. This provides an early warning of any increase in CO2 and gives the user valuable time to take action. For re-breathers that are not required to be anti-magnetic, this solution is relatively simple. However, re-breathers that are specified to comply with STANAG 2897 Class A would be compromised by the use of an off-the-shelf CO2 sensor which has a typical (i.e. relatively high) magnetic signature.

Before Analox’s prototype sensor is put into production further tests will be performed to prove its ongoing accuracy and reliability. And whilst details of the technologies involved are commercially sensitive, it is fair to say that the non-magnetic CO2 sensor offers many advantages over those currently available.

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