What type of construction is required to prevent contamination egress and ingress in the ISO Class 7 HD buffer room?

In an ISO Class 7 hazardous drug (HD) buffer room, the primary concern is to maintain the integrity of the controlled environment and prevent contamination from outside sources as well as to ensure that any potentially harmful compounds are contained. Solid hard wall construction, or 'stick-build' construction, is necessary in this context because it creates a robust barrier that prevents the ingress of dust, microbes, and other contaminants. This type of construction provides the durability required for the frequent disinfection and cleaning that is essential in handling hazardous materials, thus ensuring compliance with USP 800 standards.

Additionally, solid walls can effectively support the required airflow and pressure differentials needed in the buffer room. They also assist in containing hazardous substances within the room, safeguarding both personnel and the environment. The other construction options, such as temporary walls, soft wall options, or open-air designs, do not provide the same level of protection or environmental control, making them unsuitable for a buffer room where precise conditions must be maintained to ensure safe handling of hazardous drugs.