Very strange unexplained air loss

[SmokeAire]

I think Herman is right, you are assuming it all happened at once but as you say that seems pretty far fetched. Being they were in your car for a week, maybe they heated up, that was enough pressure to sneak by a ring or a valve that wasn't totally tight, they leaked off until they resealed (slow leak.) Then there just happened to be condensate the morning you went to use them.

Like Sherlock, look for the dog that didn't bark!

Don't you mean:
"Is there any point to which you would wish to draw my
attention?"
"To the curious incident of the dog in the night-time."
"The dog did nothing in the night-time."
"That was the curious incident," remarked Sherlock Holmes.

A more appropriate Holmesian quote is: "When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth."

I checked the temps for Fri. Here's the link:http://www.weather.com/weather/pastweather/hourly/USFL0252?stn=0&when=100804

For most of the night the air temp and dew point were the same.
I went to the car at 9:30am. The temp did increase bit over the dew point. When I touched the tanks they were a lot colder then the air temp. Nothing else in the car was wet or as cold. So I guess looking at the two temps it would not have taken a big increase in air temp to cause "dew" from forming on the tanks.
I did not hear any leakage during the week and air leaking from a tank even a small leak usually makes a detectable noise however slight.
Now I have observed when my LDS is emptying my tanks to refill them (nitrox) he opens the valve very slightly to let the air out very slowly. There is noise and it takes a quite a while. Sometimes the hissing will stop and he will have to open the valve more so the air will continue leave.
I'm not discounting a slow leak, seems to be the most likely scenerio, but I would think I would have heard it as much time as I spent in the car this past week.

Where is Mr. Holmes when you need him?

 

[Drew Sailbum]

I did not hear any leakage during the week and air leaking from a tank even a small leak usually makes a detectable noise however slight.
...

I'm not discounting a slow leak, seems to be the most likely scenerio, but I would think I would have heard it as much time as I spent in the car this past week.

Don't be so sure. While there is a sound, if the leak is slow enough the sound will be very quiet and easliy drown out by the usual road and car noises.

 

[pasley]

Speaking of being in the car all week. The high temps of being in the car is perhaps not the best storage environment for the tanks. As you have already stated, with flair I might add, the sound of a burst disk (or valve getting opened) unexpectedly can be, well, rather shocking.

 

[SmokeAire]

Well,I think the mystery is solved..almost.
I had a tank filled yesterday in prep. for todays dive. Left both of my tanks in the car over night. Just a few minutes ago (5:30am) I packed my gear and took it to the car. I opened the car door and sure enough I heard air hissing. Checked the tank that was leaking air and one of the valves(h-valves) was open very slightly. Closed the valve and checked the pressure and it was down from 3400 to 1000. The overnight low is in the upper 50's. So I'm wondering if the temp has something to do with it causing what ever friction ring keeps the valve closed tightly shrinks in cold temp and the air pressure forces the valve to open just enough to start to release the pressure. The valve that was open was not the one used to fill the tank.
Going to have to call DiveRite and ask about this. Talk about money going up in thin air.