Originally Posted by
danielchee
Some hotels don't do that due to locality fire hazard rules. I was in Stuttgart a couple of years back where the hotel says they aren't allowed to slip paper under the door. Doors were fireproof so slipping the paper under it could be a way for fire to breach the room should the paper doesn't clear the vicinity of the door completely. Don't know how true it is and even if it is, the carpet could also be a fire hazard.
BS.
If there is adequate clearance, then a minimal effort would be sufficient to push the receipt through so that it clears the door.
If the clearance is so tight that the receipt wedges under the door, then the flame associated with a burning receipt would most likely be quenched before it reached the inner side of the door.
It would not be ignited in the first place unless there was a raging fire outside the door. In which case, a slip of paper wedged under the door would be the least concern.