Hi. Welcome to Just Answer.
If it is getting on your car and inside of your home then it has to be airborn.
Are you leaving any doors or windows open?
Are you near any industrial manufacturing companies?
Does the substance have a smell?
What is the texture of it? Hard, gooey, ash like, brittle, etc.
Any additional information would be helpful.
Ok let me know if they are and what kind of manufacturing plant it is.
Your service is good
Where can I rate your svc