Did a quick visual inspection of the blower and heat strips (I got 5 of them 24kw (5+5+5+5+4).

What can I (Mr. Homeowner) do to test if all the strips (and what appear to be switches [black plastic circular]) are working OK and if all of them are coming on. Or is this job better left to HVAC folks. I know my way around a volt/ohm meter. I just need guidance on what I should/should-not be looking for.

ALSO:

I have a air leak somewhere in the return trunk near the furnace. I get this suction action if I close the door for the furnace room. As I close the door the air velocity increases at the door's edge. Prompting me to suspect the return is sucking air nearby instead of the return vents.

I have seen a hand-held device that pumps smoke into the air. It is used to detect leaks and air currents. Can this thing be purchased at a RENO type store?