How can I prove my kitchen exhaust vent egress
You can rent a &quot;fog machine&quot; or &quot;smoke (not really smoke) generator&quot; at a rental place that caters to &quot;party supplies&quot; - you can also rent a portable ventilation fan with a flexible duct. Set the fan to blow in the suspect duct and run the fog machine at its intake.
If you have smoke alarms, be aware that the smoke/fog may set them off.
Beware of using actual smoke, more than one fire has started from &quot;intentionally trying to make smoke&quot; getting out of control.