(Bismarck, ND) — A carbon monoxide leak forced the evacuation of an apartment building in Bismarck. Bismarck firefighters responded to the Boulevard Apartments late Wednesday afternoon after a carbon monoxide detector went off. First responders detected high levels of carbon monoxide on each floor and determined a faulty water heater was to blame. The water heater was turned off, and residents were allowed to return to their apartments. Nobody was injured.