I’d have thought it might be rather hazardous, especially in an enclosed area. The nitrogen displaces the air and a small volume of liquid nitrogen produces a large volume of gas, so asphyxiation could be a danger.
On the plus side, you’re going to attract the attention of the Fire Department at some point.
See? It does work.
Most methods of fire suppression have this danger. The key is to weigh the danger of asphyxiation against the danger from the fire, and use your methods accordingly.