I think there's a difference between an article of equipment being furnished by the employer and the employee's own property meant for his or her personal use. I also would consider the area it's being used in.
A $7.99 Walgreen's fan in a computer cubicle in an office? Fine, as long as it's not spliced into the back of the monitor's power cord.
20 $19 Walmart heaters being used to cure the drywall in a winter build instead of a torpedo or two? Un-uh.
