CMC Toxic Gas Detection & Monitoring Flashcards
6 cards from real CMC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CMC Toxic Gas Detection & Monitoring flashcards as text
What is the IDLH (Immediately Dangerous to Life or Health) concentration for hydrogen sulfide (H2S)?
Answer: 100 ppm
NIOSH established the IDLH for hydrogen sulfide at 100 ppm, above which escape without respiratory protection becomes impossible.
Which instrument is most commonly used to detect oxygen-deficient atmospheres in marine confined spaces?
Answer: Electrochemical oxygen sensor
Electrochemical oxygen sensors are the standard instrument for detecting oxygen-deficient atmospheres, providing continuous real-time O2 readings.
What minimum oxygen concentration must a marine confined space atmosphere maintain for safe entry without SCBA?
Answer: 19.5%
OSHA and NFPA 306 require a minimum of 19.5% oxygen by volume for an atmosphere to be considered safe for entry without supplied-air respirators.
A photoionization detector (PID) is best suited for detecting which class of compounds in marine spaces?
Answer: Volatile organic compounds (VOCs)
PIDs use UV light to ionize molecules and are highly sensitive to volatile organic compounds such as benzene, toluene, and styrene.
What does a Lower Explosive Limit (LEL) reading of 10% on a combustible gas indicator actually represent?
Answer: The gas concentration is 10% of the LEL value
A 10% LEL reading means the combustible gas concentration is 10% of the lower explosive limit — not 10% of the total atmosphere.
Which condition requires immediate evacuation of a marine confined space during monitoring?
Answer: Combustible gas at 5% LEL
NFPA 306 requires evacuation when combustible gas readings reach or exceed 10% LEL; a reading of 5% LEL warrants heightened caution but 10% triggers mandatory evacuation.