🔍 Key Concepts

• Hydrocarbon vapors are flammable gases (like gasoline, benzene, etc.) that can form explosive atmospheres • The instrument used should be designed to measure concentration of flammable/combustible gases in air • Some instruments are for oxygen level only, not for detecting specific fuel vapors

💭 Think About

• Ask yourself: which device is commonly used in tankers and confined spaces to check for explosive or flammable gas concentrations before entry or hot work? • Which option sounds like it measures the presence and amount of flammable gases rather than oxygen or general gas volume? • Think about which of these devices would be carried by personnel doing gas-freeing or before issuing a hot-work permit on a tanker.

✅ Before You Answer

• Eliminate any device whose main purpose is to measure oxygen concentration only • Eliminate devices that are for general gas volume measurement rather than specifically flammable gases • Focus on the choice that is widely associated with testing for explosive limits (LEL/UEL) of hydrocarbon vapors in tanks and confined spaces