Most semiconductor cleanrooms are ISO 4 (Class 10) or ISO 5 (Class 100) cleanrooms. However, some projects may require an ISO 6 (Class 1,000), ISO 7 (Class 10,000), or even ISO 8 (Class 100,000) cleanrooms. They must also follow the ISO 14644-1 standard. There are many variations and regulations in semiconductor cleanroom requirements, making them some of the most demanding in the industry.