The standards say 1 square inch of vent for each 1000 BTUs of propane burned: for the Wave 3, that uses 1/8 pound of propane per hour at 22000 BTU/lb, that means just under 3 square inches of vent opening.
A standard 14" ceiling vent open 1/2" will give you 3.5 square inches of venting. 2 vents, one low on the wall and one high is supposed to be best, but in practice, everybody just cranks open a ceiling vent a little.
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