Most furnaces, home or RV, will have a scorched odor when started up for the first time each winter, as the dust that has accumulated on the heating element is burned off. The smell should disappear on its own. If it doesn't disappear, then a small vacuum cleaner applied to the heating element from inside the trailer should do the trick. But vacuum the heating element after the heater has cooled down. No sense risking a burn.
Engineering: Finding complex solutions to simple problems you didn't even know you had.