As long as the product label instructions are followed and the product is only applied to places indicated on the label, the product should not be harmful to humans or pets.
Demon WP Insecticide should not be applied to any manure or compost that would be used for edibles.
Demon WP will kill Midges that come in contact with it. It cannot be applied as a broadcast, however. Talstar P would be a great product for you. Spraying a product such as Talstar P on window screens, doors, bushes, and plants around your home can act as midge repellant to keep midges away. Citronella candles or oils can act as a midge repellant, but they aren’t as effective when used alone. Talstar P is safe for children and pets after dried.
Demon WP Insecticide is a wettable powder that needs to be mixed with water. You would use 1-2 packets per gallon of water.
If an air conditioner unit was running while you were applying Demon WP, this should not affect the application if used as directed.
Demon WP Insecticide when used inside is only applied to cracks and crevices. It could be used in the drop ceiling around vents and other entry points that allow insects in.
While we cannot confirm or deny if Demon WP Insecticide can cause cancer we can say that the product is safe when used as directed on the product label per the manufacturer. People and pets should be out of the area during treatment until dry, a few hours is best. We do have the Safety Data Sheet with information that might help.
Recommendations are based on what you are treating for. Demon WP is a very good general purpose insecticide for pests like spiders, roaches, etc. Keep in mind that it can leave a white residue behind on some surfaces.
Another good option for general pest control would be Cyzmic CS. This is a liquid concentrate that is mixed with water. It will go on clear and dry clear as well. The residual indoors is 90 days and 30 days outdoors.