Glad you're okay I'm thinking the gas in that tank is LP or natural gas. I'm not sure a CO detector would be any use in that situation although they are great to have if your home is heated with a hydrocarbon fuel furnace.
CO is a byproduct of hydrocarbon combustion. Fortunately you didn't have any combustion there.
http://answers.yahoo.com/question/in...4082059AAvKWH8
Someone using a gas powered generator would definitely benefit from a CO detector.