On the opposite side of the spectrum, a pharmaceutical cleanroom will require an outward directional airflow to prevent the infiltration of "contaminated" air (or ambient air that has not been HEPA filtered). Having a positive cubic feet per minute (CFM) offset within the room does not ensure a positive pressure, nor does it ensure outward directional airflow to all adjacent spaces. On more than one occasion, we have found these rooms are being drawn positive due to a connected room that is operating under a high level of negative pressure. The positive-pressure room is actually a conduit from its ceiling space to the adjacent room, and unconditioned and unfiltered air is being induced through wall penetrations and ceiling tiles that are not properly sealed. These rooms should be constructed and sealed to ensure that the positive CFM offset provided by the HVAC systems will provide outward directional airflow to all surrounding spaces. Superior Duct Testing the Model 400x DucTester has arrived Super Lightweight. Carry to Jobsite Fast Setup & Teardown SMACNA Compliant Reporrng Sooware Easy to Use. Online Training Included Shop Online Blower Door Testing At Any Size Most powerful blower door on the market. retrotec.com www.retrotec.com | sales@retrotec.com | 1-855-738-7683 TAB Journal Summer 2019 5http://www.retrotec.com http://www.retrotec.com