Ventilation for fuel cell power unit

A method usable with a fuel cell system comprising:

• providing a first subsystem not classified to operate in a flammable environment;
• providing a sensor to detect a flammable gas;
• providing a component capable of emitting a flammable gas;
• arranging the first subsystem, the sensor and the component in an enclosure such that the component is located above the first subsystem and below the sensor;
• providing a buoyancy path to guide the emitted flammable gas out of the enclosure;
• and
• using the sensor to detect whether a concentration of the flammable gas in the buoyancy path exceeds a predefined threshold.

A vehicle, comprising:

• a chassis;
• and
• a fuel cell system comprising:
• an enclosure;
• a first subsystem not classified to operate in a flammable environment;
• a sensor to detect a flammable gas;
• and
• a component capable of emitting a flammable gas,
• wherein the first subsystem, the sensor, and the component are arranged in the enclosure such that, when the fuel cell system is supported by the chassis, a buoyancy path for emitted flammable gas to escape the enclosure is provided between the component and the sensor.