FBI Swat raids the house, and upon requested doing a second check, Alpha Leader spots a burning candle and then realizes the gas for the oven/stove is running. LP has a distinctive odor embedded chemically into them to alert to a leak or gas flowing without being burned. In addition LP is heavier than air, it would be impossible it would not have been detected by the time the volume to fill up the 3.5 ft to the counter top of the entire first floor.