Humidity & Temperature Control MCQs With Answer

This set of MCQs on Humidity & Temperature Control is tailored for M.Pharm students preparing for MIP 203T – Pharmaceutical Production Technology. It covers core concepts such as psychrometrics, dew point, HVAC roles in GMP, dehumidification strategies, instrumentation, cleanroom environmental limits, and the influence of moisture and temperature on product stability and microbial risks. The questions are designed to deepen understanding beyond definitions — emphasizing practical control methods, validation, monitoring tools, and consequences of poor control on pharmaceutical processes and excipients. Use these MCQs to test knowledge, prepare for exams, and identify areas needing further study in environmental control for pharmaceutical manufacturing.

Q1. Which definition best describes relative humidity (RH)?

• The mass of water vapor per cubic meter of air
• The ratio of actual water vapor pressure to saturation vapor pressure at the same temperature expressed as a percentage
• The temperature at which air becomes saturated
• The absolute weight percentage of water in the air

Correct Answer: The ratio of actual water vapor pressure to saturation vapor pressure at the same temperature expressed as a percentage

Q2. What is the dew point?

• The maximum humidity an air sample can hold at any temperature
• The temperature to which air must be cooled at constant pressure to become saturated and begin to condense water
• The wet-bulb temperature measured by a psychrometer
• The temperature at which microbial growth stops

Correct Answer: The temperature to which air must be cooled at constant pressure to become saturated and begin to condense water

Q3. Which statement correctly describes wet-bulb temperature?

• It is always higher than dry-bulb temperature
• It equals dry-bulb temperature when the air is saturated and indicates evaporative cooling potential
• It measures absolute humidity directly
• It is unrelated to evaporative processes

Correct Answer: It equals dry-bulb temperature when the air is saturated and indicates evaporative cooling potential

Q4. How does saturation vapor pressure change with temperature?

• It decreases as temperature increases
• It remains constant with temperature change
• It increases exponentially with increasing temperature
• It increases linearly with decreasing temperature

Correct Answer: It increases exponentially with increasing temperature

Q5. What is the primary effect of elevated relative humidity on hygroscopic pharmaceutical powders during storage?

• Increased powder porosity and improved flow
• Caking, agglomeration and reduced flowability
• Reduction in particle size due to drying
• Increased electrostatic repulsion improving mixing

Correct Answer: Caking, agglomeration and reduced flowability

Q6. Which relative humidity range is generally recommended for many sterile manufacturing areas to balance microbial control and product quality?

• 10–20% RH
• 40–60% RH
• 70–90% RH
• 0–5% RH

Correct Answer: 40–60% RH

Q7. Which of the following is NOT a primary function of HVAC systems in GMP pharmaceutical production areas?

• Control of temperature and relative humidity
• Provision of sterile filtered water for formulations
• Control of particulate levels via filtration
• Establishment of pressure differentials between rooms

Correct Answer: Provision of sterile filtered water for formulations

Q8. What is the rated efficiency of a properly installed HEPA filter at the most penetrating particle size (approx. 0.3 µm)?

• 50% efficiency
• 75% efficiency
• 99.97% efficiency
• 100% efficiency for all particle sizes

Correct Answer: 99.97% efficiency

Q9. Which parameter describes absolute humidity?

• Percentage of moisture relative to saturation
• Grams of water vapor per cubic meter of air (g/m3)
• Temperature corrected percent RH
• Relative pressure of water vapor

Correct Answer: Grams of water vapor per cubic meter of air (g/m3)

Q10. Which desiccant is most commonly used for packaging and local dehumidification in pharmaceutical products?

• Calcium carbonate
• Silica gel
• Polyethylene glycol
• Calcium sulfate dihydrate

Correct Answer: Silica gel

Q11. Which dehumidification method removes moisture primarily by cooling air below its dew point to condense water?

• Adsorption desiccant dehumidification
• Refrigeration (mechanical) dehumidification
• Membrane separation dehumidification
• Electrostatic dehumidification

Correct Answer: Refrigeration (mechanical) dehumidification

Q12. How often is performance requalification (PQ) of critical HVAC systems typically recommended in GMP-controlled areas?

• Daily during production only
• Every 10 years
• Annually (unless otherwise justified)
• Only at initial installation

Correct Answer: Annually (unless otherwise justified)

Q13. Which hygrometer type is considered the most accurate for dew point measurement and calibration reference?

• Capacitive polymer hygrometer
• Chilled‑mirror (dew point) hygrometer
• Resistive humidity sensor
• Chemical indicator strip

Correct Answer: Chilled‑mirror (dew point) hygrometer

Q14. In general, how does increasing temperature (within a biological organism’s tolerance) affect microbial growth rate?

• Growth rate decreases linearly with temperature rise
• Growth rate increases up to an organism‑specific optimum, then declines
• Temperature has no effect on microbial growth
• Growth stops immediately above 20°C for most microbes

Correct Answer: Growth rate increases up to an organism‑specific optimum, then declines

Q15. To prevent condensation on critical sterile surfaces, what environmental control strategy is most effective?

• Maintain surface temperatures below the dew point
• Maintain surface temperatures above the dew point
• Reduce air changes per hour to lower airflow
• Allow RH to rise above 90% briefly during production

Correct Answer: Maintain surface temperatures above the dew point

Q16. Approximately how much water vapor does saturated air contain at 25°C?

• About 5 g/m3
• About 23 g/m3
• About 50 g/m3
• About 100 g/m3

Correct Answer: About 23 g/m3

Q17. What is the primary use of a psychrometric chart in pharmaceutical HVAC design?

• To map particulate trajectories in cleanrooms
• To graphically determine thermodynamic properties of moist air (enthalpy, humidity ratio, dew point, etc.)
• To display HEPA filter efficiency over time
• To predict microbial contamination rates

Correct Answer: To graphically determine thermodynamic properties of moist air (enthalpy, humidity ratio, dew point, etc.)

Q18. What is a commonly recommended temperature range for personnel comfort and product stability in many pharmaceutical production suites?

• 8–12°C
• 20–24°C
• 28–32°C
• 35–40°C

Correct Answer: 20–24°C

Q19. Which of the following excipients is known for being hygroscopic and often requires strict humidity control during handling and storage?

• Magnesium stearate
• Hydroxypropyl methylcellulose (HPMC)
• Mannitol
• Microcrystalline cellulose (Avicel)

Correct Answer: Hydroxypropyl methylcellulose (HPMC)

Q20. For critical cleanroom processes, what is a typical acceptable alarm deviation for relative humidity from the setpoint before corrective action is required?

• ±0.1% RH
• ±1% RH
• ±5% RH
• ±20% RH

Correct Answer: ±5% RH

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