I tried this in my driveway to see how well it would work. I have 2 Honda's paralleled and a topper on my truck. With both side windows open, a fan in one of them and the back shut on a 85 degree day. After running about 30 minutes I opened the back to see how hot it was inside and how much the exhaust had built up and both were pretty significant. I'm not sure this would be a viable solution for several hours. Additionally, CO2 is heavier than air so using the setup described over night would dump a lot of CO2 right under the front of the trailer where you are sleeping. CO2 detectors help, but mine is located in the back half of the trailer by my fridge and furnace. Not sure it is worth the risk.