Yeah, that's Callie's goodbye thread. There's no "timer" she used in the traditional sense.
But, I've thought about this myself. It is possible. It's possible to rig up an electric winch onto some type of cart that would automatically pull some small pails of burning charcoal into a tent. You'd have to make a hole in the side of a tent and construct a "tunnel" of some sort, attached and sealed to the tent fabric. Controlling the winch would be an electric timer that could be set to turn on at a specific time, thereby allowing the winch to operate and pull the cart into the tent. Likewise, the timer could be set to turn off the winch after whatever amount of seconds is necessary to allow the cart to reach the right position in the tent. I thought about doing it this way to allow for some type of "medication" I would take to make me pass out. Of course a lot of experimentation would need to be done with this in order to get the timing all right. If, for example, I found that the meds I would take would put me out after about a 1/2 hour, I could get the charcoals burning properly, place them on the cart, take the meds, and then go inside the tent and just wait to pass out. After a half hour would pass, the timer would start, the winch would pull the cart into the tent, and once in, the timer would turn off. On it's way in, some type of "arm", mounted to the cart, would close a "door" at the entrance of the tunnel, to help contain the CO in the tent. All the while that was happening, I'd be unconscious, unaware of any of it. The reason I basically dropped the idea is I couldn't find a suitable drug that could guarantee unconsciousness within a consistent short amount of time.