ISO Class 8 is an atmospheric environment that contains less than how many particles of 0.5 microns in diameter per cubic meter of air?

ISO Class 8 is an atmospheric environment that contains less than how many particles of 0.5 microns in diameter per cubic meter of air?

• A. 3,520 particles 0.5 microns per cubic meter
• B. 352,000 particles 0.5 microns per cubic meter
• C. 3,520,000 particles 0.5 microns per cubic meter
• D. 352 particles 0.5 microns per cubic meter

Answer: (D)

This question tests understanding of ISO air cleanliness classifications for particles 0.5 microns and larger. For ISO Class 8, the limit is 3,520,000 particles per cubic meter of air. The counts increase by a factor of ten as you move to less stringent classes (ISO 7 is 352,000; ISO 9 would be 35,200,000, etc.), so 3,520,000 per cubic meter fits ISO Class 8. The other numbers would correspond to either a cleaner class (like ISO 7) or a misread of the ISO scale, since 3,520 and 352 are far too low for ISO Class 8.

This question tests understanding of ISO air cleanliness classifications for particles 0.5 microns and larger. For ISO Class 8, the limit is 3,520,000 particles per cubic meter of air. The counts increase by a factor of ten as you move to less stringent classes (ISO 7 is 352,000; ISO 9 would be 35,200,000, etc.), so 3,520,000 per cubic meter fits ISO Class 8. The other numbers would correspond to either a cleaner class (like ISO 7) or a misread of the ISO scale, since 3,520 and 352 are far too low for ISO Class 8.