mosquito repellent device; mosquito fumigator
A device that repels mosquitoes by fumigation, often using smoke or vapor. Common traditional examples include 蚊取り線香 holders.
On summer nights, I use a mosquito repellent device to keep mosquitoes away.
蚊帳 is a mosquito net, a physical barrier, whereas 蚊遣器 uses smoke or vapor to repel mosquitoes.
Compound of 蚊 (ka, 'mosquito'), 遣る (yaru, 'to send away'), and 器 (ki, 'container/device'). The reading かやりき follows standard rendaku for 器.