🔍 Key Concepts

• flammable (explosive) range – the mix of fuel and air between the lower and upper explosive limits (LEL/UEL) • difference between toxicity (harm to health) and flammability (risk of fire/explosion) • meaning of flash point – the temperature at which a liquid gives off enough vapor to ignite

💭 Think About

• Is the question asking about when vapors are toxic to breathe, or when they are likely to ignite/explode? • How does the concentration of vapor in air relate to the chance of an explosion? Consider what happens if it is too lean or too rich. • Does a flash point guarantee continuous danger, or does it relate to the conditions needed to start ignition?

✅ Before You Answer

• Identify whether the key concern in the question is explosion/ignition or poisoning. • Recall that mixtures outside the flammable range (below LEL or above UEL) will not burn, even if toxic. • Check your understanding that flash point is about the minimum temperature to produce ignitable vapors, not necessarily about whether vapors are always present.