Whats type of chain you are using? single or multi-speed chain? and chainset?

Multi-speed type chain by itself, its not problem for single speed uses if you set chain tension correctly.

Whilst single speed chain type tend to be more forgiving if you set it to be more slack and it won't fall off easily 'unless' you hit a deep pothole and your whole bike up-down like crazy, chance the chain will pop.

Also chainset, must be sure you uses the one designed for single because its safer for many reason.