deepdiver5by5 once bubbled...
I know this has been beaten on this board and by a lot of people, so lets not let my question get out of hand. I went into a shop in Toronto for air because my friend said they have the best air around the GTA (on by the way I had a fun dive on the wreck off St. Catherines this weekend). They had this certificate that previous threads have mentioned Z180. The man in the store said that this was their retest and the sample was taken at the end of the filter life.
My question is at what time of the filter life sould this air test be done? Are there standards when this should be done in the six months?
Just curious?
Only complant about their air - very dry, almost too dry.
Dive Deep
deepdiver5by5
Very good questions DD25 and ones that an informed diver should ask of their fill station manager. I'll step up to the plate first here but I am sure others will follow
Filter life is dependent on many factors such as the quality, humidity, and temperature of the ambient air, the proper functioning of the compressor which is dependent on routine maintenance, and of course how many hours the filters have been run. Running a compressor in high humidity and temperature conditions shortens filter life. A good fill station manager will record the temperture and humidity in the compressor's log and as these conditions increase the requisite time to change a filter decreases.
As far as when to change a filter the easiest indicator would be to have a Bauer Securus system which monitors the degree of saturation in the filter cartridge by measuring the humidity of the molecular sieve (drying agent). I don't know at what humidity content the system will move from the green light to the yellow light, but when this 'advance warning' appears the filter cartridge should be changed. Hopcalite which removes your CO is rendered ineffective when the humidity is above about 4% and there must be a similar value for the charcoal. The Securus system would provide a warning to change the filter well below this humidity level.
As far as when to do the air test a smart and safe fill station manager will do do his test just *before* the filter change as this will show how well the system has functioned over the life of the cartridge. If the retest in your shop was done just before the filter change then this owner knows his stuff. The result on this would represent the 'worst' air someone could get from his fill station so if this air passes and is oxygen compatible he has a very good functioning fill station. This is where the devil is really in the details as we know most fill station owners will try and take their sample soon after a filter change where the likelihood of passing the test is greatest. The air may readily pass at this point but three months later with lots of hot humid weather and say a compressor leaking oil the air might fail miserbly. A incompetent fill station manager might change the filter and then do the air test immediately afterwards not realizing that one month later because of the humid conditions and the poor quality of his compressor system that he is pumping air that would fail a test. The air test taken right after a filter change will likely pass with flying colours but to the trained eye there are ways to tell if this has been done. Basically the farther one is from the air test date on the same filter the greater chance there is for the air to fail a test likely for excessive CO2 or moisture content. An informed diver will then inquire as to when the test was done relative to the filter change. The greatest risk for a diver to get bad air is just before the filter change is done assuming the ambient air is not contaminated.
There are no standards as far as I know with regard to when one should do the six month air test relative to the filter change but maybe someone else will know. In reality, during the busy summer season some shops should be testing monthly with the number of hours their compressors are running whereas in the slow winter months the test can likely wait six months. There are some Ontario shops that pump more air on a summer long weekend than they do in three months during the winter. That CSA six month air test frequency remember is a bare bones minimum standard.
As far as having the best air in the GTA I would accept that claim if the following criteria were met:
1. An accredited lab was used (not OUC)
2. The air was tested to the 2000 version of CSA Z180.1 not 1985
3. The test was really done just before the filter change and not right afterwards
If this is the case please let us know where you purchased your air because as far as when I last checked there was only one shop in the GTA which met the first two criteria on the list.
As far as dry air in Ontario, it can never be too dry. Yes you get 'cotton mouth' but the lower the dewpoint the less likely you are to have a first stage free flow in cold water.
Hope that helps
