Grade C in ISO cleanroom classification refers to a clean area used for less critical stages in the manufacturing process of sterile products. It's not a single ISO classification but rather corresponds to two:
- At rest: Grade C is equivalent to ISO Class 7.
- In operation: Grade C is equivalent to ISO Class 8.
This means that the number of airborne particles permitted in a Grade C cleanroom varies depending on whether the equipment is running. The stricter classification (ISO 7) applies when the room is at rest, and the less strict classification (ISO 8) is acceptable during operation. This distinction is crucial for manufacturers to ensure that their cleanroom maintains appropriate cleanliness levels throughout the production process. The difference in classification reflects the increased particle generation during active manufacturing activities.
Several sources confirm this dual classification for Grade C cleanrooms, emphasizing its use in less demanding manufacturing steps where a higher level of cleanliness than in Grade D rooms is still required. This classification is widely used in pharmaceutical and other industries where controlled environments are essential. The specific particle counts for each ISO class (7 and 8) can be found in the relevant ISO standards.
Different sources may use different terminology when referring to the equivalent classifications (e.g., class 10,000 instead of ISO 7), but the underlying meaning remains the same. Note that Grade C should not be confused with the "Grade C" found in some ISO standards relating to fasteners, such as hexagon nuts and bolts (ISO 4034:2012 and ISO 4016:2011). These are separate standards and unrelated to cleanroom classifications.
