Be careful with generators

jrnymn7 wrote:
In certain cases, cracking a window and running a roof exhaust may actually draw fumes into the rv.

Yep ... that's right on. Happened to us when camping in our Class C during warm weather on Antelope Island in the Great Salt Lake. We had a window open in the back, with the roof vent fan in the front turned ON and set to blow OUT ... this brought the sickening odors of "dead stuff" into the RV from the back to the front.

That's why I said in my post above, to turn the roof vent ON and set it to blowing IN (you need a reversible roof vent fan to do this) ... with everything else closed so there is no "flow" possible inside the RV. You just get the roof vent fan "trying to blow in" but not being able to. That's where the slight air pressure build-up inside the RV comes from and how it's maintained, thus preventing any outside generator fumes - from down low where generators are - from getting inside via any small cracks or other tiny openings from less than perfect seals. This relies on "air pressure physics" to prevent carbon monoxide from getting inside, hence no worries about how well-sealed the RV is or how well blocked-off or positioned the generator might be. We have used this technique for safety when running the built-in generator and air conditioner nearly all night so we could sleep when drycamping in extreme heat and humidity. (Remember that an RV's roof air conditioner only recirculates air - it doesn't bring any new air in from the outside - so a roof air vent fan set to blow IN can still maintain positive air pressure inside while the RV's air conditioner is running.)

As I mentioned earlier, this also works well when traveling on dusty roads to keep dust out of the RV. FWIW, I think that some Australian off-road trailer manufacturers design in positive air pressure systems to keep them clean inside when traveling in dusty conditions.