An Oil Mist Detector (OMD) continuously monitors the air inside the crankcase of large engines. It looks for tiny oil droplets (mist) suspended in the air — a sign that there could be lubrication problems, overheating, leaks, or bearing failure. Elevated oil mist levels are dangerous because they can reach a flammable/explosive concentration inside the crankcase. They give advance notice of issues like bearing wear, lubrication failure, or hot spots, which can otherwise lead to severe damage. Oil mist can be highly flammable; in confined engine spaces, mist + oxygen + an ignition source (like a hot surface) can cause crankcase explosions. An OMD helps prevent these catastrophes by alerting crews early. OMD are often required by marine safety regulations (e.g., for ships with large engines and unmanned engine rooms).