Air Sampling and Instrumentation Flashcards
7 cards from real CIH practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Air Sampling and Instrumentation flashcards as text
Which sampling method is most appropriate for collecting a time-weighted average (TWA) sample of a volatile organic compound over an 8-hour shift?
Answer: Passive diffusion badge sampler
Passive diffusion badge samplers are designed for TWA sampling over full work shifts without requiring a pump.
A personal air sampler pump calibrated at 2.0 L/min drifts to 1.85 L/min by end of shift. What is the most appropriate corrective action for future sampling?
Answer: Recalibrate the pump before and after each sampling period
NIOSH recommends calibrating pumps before and after sampling to detect drift and ensure data validity.
What does the term 'face velocity' refer to in the context of a laboratory fume hood?
Answer: The inward air velocity measured at the hood sash opening
Face velocity is the inward air velocity measured at the plane of the open sash, typically 80–120 fpm for adequate containment.
Which instrument principle is used in a flame ionization detector (FID) for measuring total hydrocarbons?
Answer: Ionization of compounds in a hydrogen flame creating a measurable current
FIDs burn sampled air in a hydrogen flame; organic compounds produce ions that generate a current proportional to carbon concentration.
When sampling for respirable crystalline silica using a 10-mm nylon cyclone, the recommended sample flow rate is:
Answer: 1.7 L/min
The 10-mm nylon cyclone must be operated at 1.7 L/min to achieve the ISO/ACGIH respirable particle size-selective criterion.
A colorimetric detector tube shows a stain length of 35 mm for toluene. The tube calibration scale reads 50 ppm at 35 mm but the sample was taken at half the recommended strokes. What is the corrected concentration?
Answer: 100 ppm
Halving the number of strokes means half the required air volume was sampled, so the true concentration is twice the read value (50 × 2 = 100 ppm).
Which characteristic of a sorbent tube most directly determines its ability to retain sampled contaminants without breakthrough?
Answer: Sorbent capacity and affinity for the target analyte
Breakthrough occurs when the sorbent's capacity or affinity for the analyte is exceeded, allowing contaminant to pass through unretained.