Negatives aside, I would still have the plastic sheeting and duct tape handy. This forum is largely about being prepared for dangerous situations of low probablity of occurance. There have been numerous terrorist related inquiries and arrests here in S. Florida. If I were to look up and see a small drone airplane spraying something over my area I would dang sure seal up my safe room and wait it out for a few hours. I think four people would have no trouble breathing in a large sealed bedroom for that long. Regards, Keys