+1
I have a gravel drive and the dust lingers what seems like forever in front of my IR cameras. Kinda had me thinking the first few times it happened also.
Ever have spiders sit on the lense and have dinner~?~
I have never had them have dinner, but I do often have them try and build webs.
I hate to do it but I have to always take a broom to the web. my cameras record on motion so when they are building the web it is constantly recording.