Chemical Sampling & Analysis Techniques Flashcards
7 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 7 Chemical Sampling & Analysis Techniques flashcards as text
A Marine Chemist is testing a tank that previously carried leaded gasoline. Which additional analyte beyond standard LEL/O2/H2S/CO must be specifically addressed in the sampling plan?
Answer: Tetraethyl lead (TEL) vapors, which require specialized sampling media and laboratory analysis
Tetraethyl lead is extremely toxic and not detected by standard CGI or electrochemical sensors; it requires specific sampling media (e.g., hopcalite) and laboratory analysis.
When calculating the air concentration of a contaminant from a sorbent tube sample, the chemist must know all of the following EXCEPT:
Answer: The color of the sampling pump casing
Pump casing color is irrelevant; the calculation requires sampled air volume, analyte mass recovered, and desorption efficiency to compute the true concentration.
In marine confined space entry work, what distinguishes an IDLH (Immediately Dangerous to Life or Health) concentration from a Ceiling value?
Answer: IDLH is the concentration posing immediate escape impairment or irreversible health effects; Ceiling is the maximum concentration that must never be exceeded at any instant
IDLH defines the upper limit for safe emergency self-rescue without impairment, while a Ceiling is an instantaneous maximum that must never be exceeded during any brief exposure.
Which of the following best describes the purpose of using a midget impinger when sampling for reactive gases such as chlorine in a marine atmosphere?
Answer: The reactive gas is absorbed into a liquid reagent solution, stabilizing it for wet chemical or spectrophotometric analysis
Midget impingers collect reactive gases by bubbling sampled air through a selective absorbing solution, chemically stabilizing the analyte for accurate quantitative analysis.
A Marine Chemist performing pre-entry atmospheric testing finds that the multi-gas monitor's H2S sensor is reading erratically. The most appropriate immediate action is:
Answer: Remove the instrument from service, substitute a calibrated backup instrument, and do not proceed with entry testing until a reliable sensor is confirmed
An erratically reading sensor cannot be trusted; using a certified backup instrument is the only way to ensure the H2S hazard is properly characterized before authorizing entry.
When monitoring for toxic vapors in a space using a photoionization detector (PID), the instrument's ionization potential (IP) of the lamp must be:
Answer: Higher than the ionization potential of the target compound for the lamp to ionize and detect it
A PID lamp ionizes compounds whose ionization potential is lower than the lamp's output energy; if the lamp IP is too low, the target molecule will not be ionized and will go undetected.
Under NFPA 306, a Marine Chemist must sample the atmosphere at multiple vertical levels within a tank. The primary reason for this requirement is:
Answer: Different vapors have different densities and may stratify, creating pockets of hazardous concentrations at various heights that a single-point sample would miss
NFPA 306 mandates multi-level sampling because vapor stratification based on density differences can create dangerous pockets that a single representative sample may not detect.