Laminar Airflow Workbench: Proper Operation for PTCE Prep

What Is a Laminar Airflow Workbench?

A laminar airflow workbench (LAFW) is the primary engineering control used for compounding sterile preparations. It provides a stream of HEPA-filtered ISO Class 5 air that sweeps over the work surface to maintain a sterile environment. Proper LAFW operation is essential for patient safety and is a key topic on the PTCE.

Horizontal vs Vertical Airflow

• Horizontal LAFW - Air flows from the back of the hood toward the operator. Used for non-hazardous sterile compounding. The most common type in hospital pharmacies for routine IV admixtures.
• Vertical LAFW (Biological Safety Cabinet) - Air flows from the top downward. Used for hazardous drug compounding and biologics. Protects both the product and the operator.

First Air

First air is the HEPA-filtered air that has not yet contacted any objects in the hood. It is the cleanest air available. Always position critical sites (vial tops, needle hubs, syringe tips, IV ports) in first air, facing the HEPA filter. Never place objects between the HEPA filter and a critical site, as this creates a zone of turbulence that can introduce contamination.

Zone of Turbulence

Any object placed in the airflow path creates turbulent air downstream. In a horizontal LAFW, this means behind the object (between the object and the operator). Items should be placed at least 6 inches inside the outer edge of the hood and spaced so they do not disrupt airflow to adjacent critical sites.

Cleaning Procedures

• Turn on the LAFW at least 30 minutes before use
• Clean all interior surfaces with sterile 70% isopropyl alcohol
• Clean from back to front, top to bottom (clean to dirty)
• Clean the work surface using side-to-side strokes moving from back to front
• Clean between each preparation and after any spill
• Do not spray directly onto the HEPA filter

Common Mistakes to Avoid

Never cough, sneeze, or talk directly over the work surface. Never place non-essential items in the hood. Never work with the sash at an incorrect height. These basics prevent contamination of sterile preparations.

LAFW operation questions appear in the PTCE patient safety domain. Know the principles of aseptic technique cold.