Other than smoke and toilet tissue, are there other ways to detect slight air movement?
The problem with smoke (I used an incense) is that it works great detecting horizontal or strong downward air movement, but not so good detecting weak, vertical air movement since the smoke rises up anyway.
Toilet tissue works well detecting upward air movement, but needs stronger air to cause any visible movement.
I need to do this after I hired a contractor to seal my HVAC ducts in the crawlspace. I want to show them the ducts are not 100% sealed by turning on all ventilation fans in my house (to create a vacuum effect inside), and showing them there is air coming out of all floor registers. Although I am able to cause slight movement with the toilet tissue test, I like something with stronger indication.