ISO Class 7 is an atmospheric environment that contains less than how many particles of 0.5 microns in diameter per cubic meter of air?

ISO Class 7 is an atmospheric environment that contains less than how many particles of 0.5 microns in diameter per cubic meter of air?

• A. 352,000 particles 0.5 microns per cubic meter
• B. 3,520 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: (A)

Air cleanliness classifications define how clean the air must be by setting the maximum number of particles of a given size allowed in each cubic meter. For 0.5-micron particles, ISO Class 7 limits are 352,000 particles per cubic meter. So an ISO Class 7 environment must have fewer than 352,000 particles of 0.5 microns or larger in each cubic meter of air. The other numbers correspond to neighboring ISO classes (higher or lower cleanliness) and would apply to those classes, not Class 7.

Air cleanliness classifications define how clean the air must be by setting the maximum number of particles of a given size allowed in each cubic meter. For 0.5-micron particles, ISO Class 7 limits are 352,000 particles per cubic meter. So an ISO Class 7 environment must have fewer than 352,000 particles of 0.5 microns or larger in each cubic meter of air. The other numbers correspond to neighboring ISO classes (higher or lower cleanliness) and would apply to those classes, not Class 7.