When Zale and the corpsman were starting to build a fire to burn the contaminated Chinese uniforms, they're building it uncontained in the middle of the compound. This sort of disposal fire (and its augmented bonfire) would've been built far away from the flammable tents and buildings of the camp.
The ashes and debris of the bonfire are much too small for the amount of material that formed it.
When Col. Potter is asking Maj. Freedman to see some of the staff on an informal basis, the rest of the camp are in the mess tent, eating dinner. However, crickets can be heard while Potter and Freedman are talking, which means it's late spring or summer. But it is also completely dark outside. At Uijeongbu's latitude, full darkness during this time doesn't come until well after 8 PM to past 9 PM -- which is far later than the usual dinnertime for a field mess hall.
The 4077th M.A.S.H. is in a war, near the front lines. The last thing they would do is light a giant bonfire at night in the middle of the camp, which can be seen for miles and make them a target for snipers or artillery. They would have done it during daylight hours, away from the camp to make sure the fire didn't damage any buildings.
When Sydney takes off his pants to throw them on the bonfire, he is wearing shoes, instead of army boots, probably to make it easier to take off the pants.
Major Freedman explains to Hawkeye the rationale for treating patients close to the front. He had already done this some months ago ( with the same character actor no less) when he suggested Hawkeye had the ability to treat another hysterical paralysis patient.