During structural fumigation, trained applicators will come into your home and spray sulfuryl fluoride everywhere. The point of this is so that the gas can be as thorough as possible by getting into every nook and cranny of your home. You’ll need to leave all doors, drawers and chests unlocked so that the gas can make its way in. It’s not uncommon for pests such as bed bugs and termites to make their way into these places.
In order to keep the toxic gas contained, a large, colorful tarp will be placed over the building, and warning signs will be put up so that no one accidentally goes inside. As an extra precaution, you could let the neighbors know in advance that you will be fumigating.
On the inside of the home, you’ll need to make sure anything living is out. This means plants and pets. Your goldfish would not likely fare well amongst the sulfuryl fluoride fumes. Any food that you leave in the house should be double-bagged and sealed. Bags made from nyloflume plastic are recommended for protection against toxic gas.
Once the fumigation is complete, the building will be aerated by the applicator, and they’ll have to do air monitoring to make sure it’s safe for you to return. The toxic gas levels must be under 1 part per million for it to be safe.
To answer your question, structural fumigation is toxic, but completely safe if everything is done within standards. Sometimes the only way to get the pests out is to fumigate, but you can rest assured that it is for the good of you and your family.