Propane Alarm Beeping

[Jude]

2018 Casita, 2 months old.
We left the inside hot water heater switch on during 4 hour drive home.
Hot and humid, all windows were closed.
Got home, inside propane alarm beeping -the one under the dinette.
We shut off hw heater and turned off gas ( refrig).
Alarm went off -Yeeeeeesh
Now-
Thoughts on how to determine which one caused the problem?
We’ve started wading through all of the posts for similar concerns, but haven’t seen this.
Thank you, thank you.

[John in Santa Cruz]

Gonna guess the HW heater kept blowing out. I've always made a point of switching those off, along with the water pump... fridge has stayed on propane without issues.

other things that can set off the propane alarm are hydrogen gas venting from wet cell batteries that are being charged too aggressively (that would be unlikely on a Casita due to the external battery cave), any sort of aerosol or other 'fragrant' product inside, even outgassing from 'new' foams and fabrics. I had to constantly get after my wife to stop her from putting boxes under the bed blocking the propane alarm.... those waxed fruit/produce boxes Costco often uses to pack your groceries seem to outgas some.

a gassy dog can even set off the alarm.

[WizWid]

Originally Posted by Jude

2018 Casita, 2 months old.
We left the inside hot water heater switch on during 4 hour drive home.
Hot and humid, all windows were closed.
Got home, inside propane alarm beeping -the one under the dinette.
We shut off hw heater and turned off gas ( refrig).
Alarm went off -Yeeeeeesh
Now-
Thoughts on how to determine which one caused the problem?
We’ve started wading through all of the posts for similar concerns, but haven’t seen this.
Thank you, thank you.

My guess is "hot" did it.
Off gassing from all that newness.

Leave a vent open next time and try again....

[Darwin Maring]

The problem with a slow leak is that the bad smell goes away and you are left with a propane bomb just waiting to go off. You are smart to have that gas detector.

ME, I always travel with the gas turned off at the tank.

[Byron Kinnaman]

Sounds like something that needs professional assistance.

[Borrego Dave]

Jude, it only takes around ten minutes to heat a tankful of water. I've never left the heater on other than just before needing it. Might want to think about not having the water heater on while traveling too. The flame is like a blow torch as compared to the reefer's. I know of a couple RVs that burned down from the flame being sucked outside while on the road. Kind of looks like a top fuel dragster with the candles lite .

[Spongelander]

I'd put my money on the water heater blowing out. We never run ours while traveling. The fridge flame is small, and we've never had ours go out in 8,000 miles of travel with it on.
The propane alarms are quite sensitive; another possibility could be plasticizers baking out of cushions, etc. in the hot weather. That possibility would probably take care of itself in a short time (it's that "new car" smell.)

[Roamer]

Is this a really old boiler? The modern boilers are able to turn the gas on and off. Leaving it on will not cause gas to escape.
All, new and old, will have a thermocouple that, unless it gets hot from a flame, will not allow the gas to flow. This is the reason you have to hold that button in on your fridge when lighting, it over-rides the thermocouple until the gas-fed flame heats it up.
The old boilers with the standing pilot lights I know less about.

On this subject, hijack…
If I smell propane gas and the alarm does not go off, then what can i conclude? Gas is not significant to set off alarm, or alarm broke?