What is Laminar Flow?
Laminar flow refers to the smooth, orderly movement of a fluid in a single direction, with minimal mixing (turbulence) between layers. In laminar flow, air moves in a uniform parallel direction, like sheets sliding past each other.
The flow of a fluid is defined to be laminar if the Reynold’s number of the flow falls within a certain range. Reynold’s number is a measurement of the level turbulence, and is dependent on the flow speed, density of the fluid, viscosity of the fluid, and the characteristic linear dimension of the geometry.
To grasp the significance of laminar flow, it's essential to contrast it with turbulent flow, its chaotic counterpart. In turbulent flow, fluid movement is characterized by irregular fluctuations, swirling patterns, and intense mixing between different layers of the fluid. This chaotic behavior
often occurs at higher velocities or in the presence of obstacles that disrupt the flow.
Understanding Laminar Flow Hoods
Simply, a laminar flow hood is a specialized enclosure designed to provide a continuous laminar flow of clean air over a workspace, typically a flat surface where experiments or procedures are
performed. The main components of a laminar flow hood are the blower fan, the high-efficiency particulate absorbing (HEPA) filter, and the enclosure itself.
The blower fan allows for consistent, controlled airflow through the system, while the HEPA filter removes airborne contaminants, creating a sterile environment for various applications, including mycology, pharmaceutical manufacturing, and medical procedures. HEPA filters are
incredibly efficient, capable of trapping particles as small as 0.3 microns with high precision. As air is drawn through the filter, it is purified, removing dust, microbes, and other potential sources
of contamination. Once filtered through the HEPA filter, air is then directed in a laminar flow pattern, creating a
sterile environment around the workspace and - preventing contaminants from settling on materials, equipment, and samples. This laminar flow pattern is achieved through carefully controlling certain variables, such as the rate of airflow, geometry of the enclosure, and HEPA
filter specifications. Laminar flow through the HEPA filter is vital in a flow hood, as turbulent flow causes mixing at the boundaries between the purified air and the surrounding contaminated air, leading to contaminants infiltrating the sterile workspace.

Parameters for Laminar Flow in a Laminar Flow Hood
The parameters for laminar air flow have been standardized by the International Organization for Standardization (ISO). ISO 14644 is a comprehensive set of standards established by ISO to
address the design, classification, operation, and monitoring of controlled environments.