- You would need a significantly larger amount of charcoal to produce enough CO to reach the required levels, but yes, it's possible.
- burning propane or butane (with a camp stove for example) also creates CO.
- it might get quite hot inside the trailer with multiple CO sources producing heat as a byproduct.
- Make sure to deactivate any pre-installed fire alarm and CO sensors.
- creating a good seal is important because trailers are not built to be airtight. Since you have to use plastic sheeting and duct tape anyway, you might as well tape off a smaller area to make it easier to reach the high CO levels needed.