Mr buddy heater

To each his own, but comming from someone in the HVAC trade for close to 30 years that has seen people die from using these types of unvented heaters I would not advise using them in an enclosed space. It is a fact that burning anything uses oxygen so even a blue flame burner will start making carbon monoxide as the oxygen in a space is used up. This depends on the cubic feet in the space and how tight the construction is. Also I would not use a CO alarm as a guide that something is not making CO, most of them do not detect lower levels that can start to affect a persons cognitive abilities. There are always going to be people that say well I did it and I am still here, well just look up CO deaths and see how many are not here any more.