swamp diver
Contributor
Tamas I can see your engineering background coming through here, but you are attempting to put the horse back in the barn with the personal filter idea when the CO door needs to be kept shut in the first place.
A couple points. 3M the large Minnesota company has already manufactured nano-based gold CO oxidcation catalysts for CBRN respirator cartridges. The problem is cost.
Both myself and DandyDon have purchased the Personal CO monitor and I do not recommend it. First off it is not waterproof and so even a slight salt spray on a boat will kill the device. The battery compartment and circuit board are wide open to the elements. Secondly it has very poor battery life and I found a month of heavy use was all you'd get. Thirdly taking a reading was a 3 minute affair with plastic zip bag and all. And lastly if one purchased the calibration kit and calibrated at the frequency indicated the cost was the same as an Analox EII CO analyzer, a far superior diver-dedicated analyzer.
There were a lot of other more complex problems such as the sensor was unfiltered and cross-reacted to everything in the environment from methanol windshield washer fumes, Sharpie marker fumes, nitric oxide during the summer in traffic, etc. Also the accuracy and precision of the analzyer was suspect in very high humidity and high temperature environments where we often like to dive.
It is a great little unit though to put on one's key chain to use at 1 atm but not a great unit for diving.
In an ideal world we should be able to prevent CO from ever getting into a diver's fill by using the following lines of defense.
Primary
1. Compressor inlet placement: keep away from all potential sources of CO such as vehicular traffic, boat exhaust, etc.
2. Compressor installation: since the most common source of CO is an overheated compressor dieseling the compressor oil, one needs to have a large air space around the compressor to prevent overheating and if necessary add mechanical ventilation. Once you examine enough compressor installs around the planet you'll see poor installations are the number one problem for CO production. Compressors if hot enough will auto-ignite the lubrication oil.
3.Oil Choice: use only a high quality compressor and oil manufacturer approved "synthetic" lube oil with high flash point. Change the oil out at compressor manufacturer recommended intervals which are even shorter if pumping nitrox.
Secondary
1. Catalyst bed: all purifiers should have a catalyst bed within. Most of the CO contamination found is coming from electrically-driven compressors so having a CO catalyst bed (Carulite, Hopcalite, Monoxycon, etc.) bed in these compressor purifiers is just as important as on the gas-engine driven compressors
Tertiary
1. Compressor CO Monitor: these are now available from Analox and other manufacturers for a reasonable price (~$1000) with the needed accuracy and MDL for compressed breathing air applications. Here in Canada all commercial dive operations and fire halls must now have a CO monitor on their compressors.
2. Diver portable CO analyzer: since the vast majority of dive compressors are poorly installed and maintained with no inline CO monitor it is incumbent on the diver to carry some sort of self-protection device, however if the simple primary preventative measures above were undertaken such a device might not be required.
A personal filter is not going to offer much protection as the catalyst bed could be easily over-whelmed with large CO concentrations or inactivated by excessive moisture when using one of the older Cu, Mn oxide catalysts. Bed volume size and dwell time may also be an issue.
A couple points. 3M the large Minnesota company has already manufactured nano-based gold CO oxidcation catalysts for CBRN respirator cartridges. The problem is cost.
Both myself and DandyDon have purchased the Personal CO monitor and I do not recommend it. First off it is not waterproof and so even a slight salt spray on a boat will kill the device. The battery compartment and circuit board are wide open to the elements. Secondly it has very poor battery life and I found a month of heavy use was all you'd get. Thirdly taking a reading was a 3 minute affair with plastic zip bag and all. And lastly if one purchased the calibration kit and calibrated at the frequency indicated the cost was the same as an Analox EII CO analyzer, a far superior diver-dedicated analyzer.
There were a lot of other more complex problems such as the sensor was unfiltered and cross-reacted to everything in the environment from methanol windshield washer fumes, Sharpie marker fumes, nitric oxide during the summer in traffic, etc. Also the accuracy and precision of the analzyer was suspect in very high humidity and high temperature environments where we often like to dive.
It is a great little unit though to put on one's key chain to use at 1 atm but not a great unit for diving.
In an ideal world we should be able to prevent CO from ever getting into a diver's fill by using the following lines of defense.
Primary
1. Compressor inlet placement: keep away from all potential sources of CO such as vehicular traffic, boat exhaust, etc.
2. Compressor installation: since the most common source of CO is an overheated compressor dieseling the compressor oil, one needs to have a large air space around the compressor to prevent overheating and if necessary add mechanical ventilation. Once you examine enough compressor installs around the planet you'll see poor installations are the number one problem for CO production. Compressors if hot enough will auto-ignite the lubrication oil.
3.Oil Choice: use only a high quality compressor and oil manufacturer approved "synthetic" lube oil with high flash point. Change the oil out at compressor manufacturer recommended intervals which are even shorter if pumping nitrox.
Secondary
1. Catalyst bed: all purifiers should have a catalyst bed within. Most of the CO contamination found is coming from electrically-driven compressors so having a CO catalyst bed (Carulite, Hopcalite, Monoxycon, etc.) bed in these compressor purifiers is just as important as on the gas-engine driven compressors
Tertiary
1. Compressor CO Monitor: these are now available from Analox and other manufacturers for a reasonable price (~$1000) with the needed accuracy and MDL for compressed breathing air applications. Here in Canada all commercial dive operations and fire halls must now have a CO monitor on their compressors.
2. Diver portable CO analyzer: since the vast majority of dive compressors are poorly installed and maintained with no inline CO monitor it is incumbent on the diver to carry some sort of self-protection device, however if the simple primary preventative measures above were undertaken such a device might not be required.
A personal filter is not going to offer much protection as the catalyst bed could be easily over-whelmed with large CO concentrations or inactivated by excessive moisture when using one of the older Cu, Mn oxide catalysts. Bed volume size and dwell time may also be an issue.
