10. What concentration of flammable vapor should activate the alarms of fixed vapor detection system stipulated in IGC Code (International Gas Carrier Code)? (A) When the vapor concentration reaches 10% of the lower flammable limit. (B) When the vapor concentration reaches 20% of the lower flammable limit. (C) When the vapor concentration reaches 30% of the lower flammable limit. (D) When the vapor concentration reaches 40% of the lower flammable limit.