Isolators must always be operated with positive pressure with respect to the room.

• A. True
• B. False
• C. Depends on design
• D. Not applicable

Answer: (B)

Isolators are designed to control where air flows relative to the room, and the pressure relationship is chosen to match the containment goal. You don’t always want air to push outward from the isolator into the room; sometimes you want to prevent anything from escaping the isolator.

If the aim is to protect the contents inside the isolator from room air (for example, maintaining a sterile or pathogen-free environment), the interior is kept at a higher pressure than the room. This positive pressure causes any leaks to flow outward, reducing the chance that room air can enter the isolator and contaminate what’s inside.

If the aim is to prevent materials or aerosols from inside the isolator from reaching the room (containment), the interior is kept at a lower pressure than the room. This negative pressure pulls room air in through leaks rather than letting contents escape, helping to contain any hazardous material.

Because both approaches are used depending on purpose and design, isolators must not be assumed to operate with positive pressure relative to the room in all cases. Always refer to the specific isolator’s design and operating procedures.