The active ingredient used in this system and others like it is pyrethrum. Touted as perfectly safe or harmless, it really isn't.

I wouldn't use it if: you have children or pets, enjoy birds and other wildlife (birds, fish, frogs, toads, etc., are aged or not in great health, are taking any medications that make your liver work extra hard, imbibe alcohol on a frequent basis, live near a water source. Many people have allergic or asthmatic reactions to this family of chemicals, and skin sensivities, too.

Spraying something like this upon occasion isn't so bad. But employing an instrument that sprays it night after night....makes me cringe to think of it. Humans shouldn't be exposed to a chemical pesticide on a chronic basis, let alone the surrounding environment.

Is your girlfriend afraid of all spiders, or everything with more than 4 legs? Some people are. Phobias can be debilitating and I sympathize with those who suffer. I'm a 'recovering arachnophobe', myself! But I wouldn't allow someone's unreasonable fear (and that's what a phobia is)to dictate that I spray volumes of toxic chemicals around a lakeside home.

Here is a link that might be useful: Information about pyrethrins

Pyrethrins are broad spectrum poisons that are made from certain cultivars of chrysanthemum plants. Used judiciously the poison can be helpful in controlling certain insect pests, but sprayed as this system does it will do more environmental harm than good.