Vented heaters are supurb. If you feel different most likely your being poisened. Get out and get fresh air immediately.
This is nothing to play around with, if you get a headacke, your in trouble, again fresh air now.
You can check your connections by spraying dishsoap and water on the gas connections to check for leaks. It will bubble.
If you use propane heaters in shanties, go out and get fresh air often , just do it.
Any other safety tips will only help educate people on how dangerous propane heaters are, there made for the outdoors and say so on the box when you buy them, beware protect your self and your children from this danger.
Post a tip here to ensure safe fishing.
You can use a carbon monoxide detector in the shanty, i bet it will be going off alot.
h2o<-------say's this poison is odorless!!!!!!BEWARE