Open the windows and the vent fan. Open all the stove burners, once you smell the gas close all the burners and wait a minute or two so the gas clears. Then start one burner and try to light it, it will still take a minute to light usually. Once the stove lights most of the gas line will be purged.
Try your heater, it may still take a few times to light but the stove will purge it out quickest.
Now-2014 Sierra 346RETS 5er BUB
Then-2002 Keystone Springdale 286RLDS TT
Nights camped in 2014-28, 2015-127, 2016-10