These long-lasting mosquito briquettes help keep your outdoor spaces mosquito-free for up to 90 days each. Simply drop one into pools, rain barrels, bird baths or other standing water up to 200 litres, and the larvicide targets mosquito larvae without harming beneficial insects. As a 100% Canadian owned company established in 1997, Doktor Doom products provide effective, non-toxic pest control solutions for your home and garden. These 4 briquettes in each pack help you enjoy time outdoors without mosquito bites.