Initial helmet testing was carried out using a 3M-Versaflo S-533L helmet (as pictured on the following page). When used to provide protection from airborne contaminants or pathogens, the helmet is connected to a portable air pump that delivers filtered air at a rate of ~200 liters/ min.
To test the helmet’s suitability as a replacement for the Exit bag, the helmet was positioned over a mannequin. The inlet was connected to a 2-liter cylinder of compressed nitrogen. Using a Max Dog flow-regulator, the delivery rate was set at the 25 liters/min (the maximum setting on the regulator). The composition of the gas was sampled at a position near the nose using a RKI Eagle gas analyser (see following diagram).
Upon switching on the nitrogen, there was a rapid drop in the level of oxygen within the helmet. Within 30 seconds, the [O2
level had dropped from ambient 21% to less than 1%. A deep breath taken by a person wearing the helmet would result in immediate loss of consciousness and rapid death. As in the case of the plastic Exit bag, the flow of nitrogen exiting the helmet from around the neck ensures that there is no build-up of carbon dioxide [CO2] within the helmet.
A video of the test procedure is shown.
The 3M mask is available from Amazon for around $85 https://www.3m.com/3M/en_US/p/d/v000094208/
Further tests are currently underway examining the possible modification of the MicroClimate Air (pictured lower left).