Ditto not a dumb question! That's what is so wonderful about this forum--we don't know and we ask, and community comes to our rescue! Thanks to you for asking--I learned several things from your question:
1. Propane is heavier than air and pools downward.
2. There are horizontal and verticle valves available
3. Propane should never be stored indoors (like I've done in my basement---yikes!!)
Thanks again for the intelligent question!
"Always the beautiful answer who asks a more beautiful question."
e. e. cummings