Which ISO Class indicates a less stringent requirement for particulate matter?

The ISO classification system for clean rooms and controlled environments categorizes areas based on the number and size of particles permitted per volume of air. In this system, each class number corresponds to increasingly stringent requirements regarding particulate matter.

Choosing ISO Class 8 indicates a less stringent requirement as it allows for a higher concentration of particles compared to the other classes listed. Specifically, ISO Class 8 permits up to 3,520,000 particles of size 0.5 micrometers or larger per cubic meter of air, which is significantly more than the limits set for ISO Class 5, 6, and 7.

By understanding the hierarchy of ISO classes, one can clearly see that the lower the class number, the stricter the limitations on particulate count. Therefore, selecting ISO Class 8 confirms that it represents a classification with the least restrictive standards, making it the correct choice in this context.