Air compression and sterilization MCQs With Answer

This set of MCQs on Air Compression and Sterilization is tailored for M.Pharm students studying Bioprocess Engineering and Technology. It covers core principles of compressed air systems used in pharmaceutical facilities — compressor types, thermodynamic aspects, air treatment and quality standards — as well as sterilization methods, validation concepts and routine tests for steam, dry heat, filtration and gaseous sterilants. Questions emphasize applied knowledge needed for designing, qualifying and operating compressed air and sterilization systems to meet regulatory and aseptic manufacturing requirements. Use these MCQs to test understanding and prepare for viva, exams or practical validation tasks.

Q1. Which compressor type is classified as a dynamic (kinetic) compressor commonly used for high flow, low to moderate pressure applications?

• Reciprocating compressor
• Rotary screw compressor
• Centrifugal compressor
• Vane compressor

Correct Answer: Centrifugal compressor

Q2. What is the primary purpose of intercoolers between stages in a multi-stage reciprocating or screw compressor?

• Increase the polytropic exponent
• Reduce the volumetric flow by condensing oil
• Lower gas temperature to reduce work and improve efficiency
• Prevent backflow to the suction line

Correct Answer: Lower gas temperature to reduce work and improve efficiency

Q3. Which of the following best describes “isothermal compression” compared with adiabatic compression?

• Temperature of gas rises significantly during compression
• Heat is removed continuously so temperature remains approximately constant
• Compression occurs without any heat transfer to surroundings
• Work required is greater than for adiabatic compression

Correct Answer: Heat is removed continuously so temperature remains approximately constant

Q4. For pharmaceutical compressed air intended for contact with product or critical equipment, which ISO standard specifies compressed air quality classes?

• ISO 9001
• ISO 14644-1
• ISO 8573-1
• ISO 13485

Correct Answer: ISO 8573-1

Q5. Which air treatment device is most suitable to achieve sub-zero dew point and lowest residual moisture for dry compressed air systems used in sterile operations?

• Refrigeration dryer
• Coalescing filter
• Desiccant (adsorption) dryer
• Aftercooler

Correct Answer: Desiccant (adsorption) dryer

Q6. Which organism is the standard challenge microorganism used to validate sterilizing-grade membrane filters (0.22 µm) for bacterial retention?

• Geobacillus stearothermophilus
• Bacillus subtilis
• Brevundimonas (Pseudomonas) diminuta
• Staphylococcus aureus

Correct Answer: Brevundimonas (Pseudomonas) diminuta

Q7. Which daily test is specifically used to detect inadequate air removal or steam penetration in pre-vacuum autoclave cycles?

• BI (Biological Indicator) incubation
• Bowie-Dick test
• Bubble point test
• Helium leak test

Correct Answer: Bowie-Dick test

Q8. In moist heat sterilization, the F0 value is the equivalent sterilization time at 121°C. What is the commonly used z-value (temperature change for tenfold change in D-value) assumed when calculating F0?

• 6°C
• 10°C
• 20°C
• 1°C

Correct Answer: 10°C

Q9. Which biological indicator organism is most appropriate for validating a steam autoclave (moist heat) sterilization cycle?

• Bacillus atrophaeus
• Escherichia coli
• Geobacillus stearothermophilus
• Pseudomonas aeruginosa

Correct Answer: Geobacillus stearothermophilus

Q10. Which sterilization method is most appropriate for heat- and moisture-sensitive single-use plastic components typically used in aseptic processing?

• Autoclaving at 121°C
• Dry heat at 160°C
• Filtration through 0.22 µm sterilizing-grade membrane
• Boiling in water

Correct Answer: Filtration through 0.22 µm sterilizing-grade membrane

Q11. Which integrity test is commonly used as a non-destructive method to verify the integrity of sterilizing-grade membrane filters after filtration and prior to use?

• Bubble point test
• Culture-based sterility test
• Gram staining
• Autoclave tape indicator

Correct Answer: Bubble point test

Q12. What is the typical acceptable Sterility Assurance Level (SAL) for terminal sterilization of pharmaceutical products and sterile medical devices?

• 10^-3
• 10^-4
• 10^-6
• 10^-9

Correct Answer: 10^-6

Q13. Which compressor lubrication approach is preferred where product-contact air must be free of oil contamination and where downstream sterilizing equipment is used?

• Oil-lubricated compressor with coalescing and oil-separator filters
• Water-sealed compressor
• Oil-free (dry) compressor
• Any compressor with refrigerated dryer

Correct Answer: Oil-free (dry) compressor

Q14. What is the main function of a coalescing filter in a compressed air treatment train for pharmaceutical use?

• Remove dissolved gases from air
• Remove aerosolized oil and fine liquid droplets
• Reduce air pressure before point-of-use
• Remove microbiological contaminants by size exclusion at 0.22 µm

Correct Answer: Remove aerosolized oil and fine liquid droplets

Q15. Which dry heat sterilization biological indicator organism is commonly used to validate dry heat ovens?

• Geobacillus stearothermophilus
• Bacillus atrophaeus (formerly Bacillus subtilis var. niger)
• Pseudomonas diminuta
• Streptococcus faecalis

Correct Answer: Bacillus atrophaeus (formerly Bacillus subtilis var. niger)

Q16. During sterilizing filtration of a parenteral solution, which quality control test demonstrates filter integrity after filtration and before aseptic transfer?

• Bubble point or diffusion (pressure hold) integrity test
• pH measurement of filtrate
• Conductivity test
• Endotoxin test

Correct Answer: Bubble point or diffusion (pressure hold) integrity test

Q17. Gamma irradiation is used for terminal sterilization of some pharmaceutical disposables. What is a commonly used sterilization dose for many medical devices and single-use components?

• 1–2 Gy
• 25 kGy
• 1000 kGy
• 0.1 kGy

Correct Answer: 25 kGy

Q18. Which statement most accurately describes the D-value in sterilization science?

• Time required at a given temperature to increase microbial population by 10-fold
• Temperature increase necessary to reduce D-value by one logarithmic cycle
• Time required at a specified condition to achieve one log (90%) reduction of a microbial population
• The fraction of spores surviving after sterilization expressed as SAL

Correct Answer: Time required at a specified condition to achieve one log (90%) reduction of a microbial population

Q19. Ethylene oxide (EO) sterilization is effective for heat-sensitive materials. Which of the following is a critical control and post-process requirement unique to EO sterilization?

• Immediate use after aeration without delay
• Minimal humidity is required and no aeration is necessary
• Extensive aeration is required to remove toxic EO residues
• No biological indicators exist for EO validation

Correct Answer: Extensive aeration is required to remove toxic EO residues

Q20. For compressed air supplied to aseptic filling lines, what is the recommended point-of-use protection to ensure sterility of supplied air contacting sterile areas?

• High-efficiency particulate air (HEPA) filter for gases
• 0.22 µm sterilizing-grade filter installed at point-of-use with validated integrity
• Activated carbon filter only
• Refrigeration dryer at point-of-use

Correct Answer: 0.22 µm sterilizing-grade filter installed at point-of-use with validated integrity

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