okay, I'll nibble. A flea collar to do exactly what? I installed a Camco screen over our trailer's hot water heater vent specifically to keep dirt daubers from building nests inside the compartment. (Learned the hard way some years ago from dirt daubers nesting inside the upstairs furnace flue to do the same!)
Seems to me a screen will do this job perfectly year after year, when a flea collar has long lost its effectiveness. ...
Then again if you have issues with fleas in the hot water heater area, this makes perfect sense!
2014 Chevrolet Silverado 3500HD Crew Cab, long box, Duramax and 3.73, SRW
Equal-i-zer 1k WDH, 2013 White Hawk 27DSRL
Los Madrones, a little slice of Texas hill country heaven