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What is the origin of the CG distributor? - Pharmaceutical HVAC
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What is the origin of the CG distributor?



A few months ago, a colleague from Process working in a frame loader system for vials, to be carried to a lyophilization room under laminar flow, asked me what CG stands for.

Honestly, I did not know the answer. Although I have been working with laminar flows for many years, I never asked me to myself about the origin of the acronym “CG”. So, I decided to investigate.

But… What is a CG distributor?


A CG distributor is a textile fabric installed normally after a HEPA filter in unidirectional flow (displacement airflow) with a very thin mesh. The function of this mesh is to provide a laminar flow of air. That means, with a velocity of 0.45 m/s (plus minus 20%).

Detail of a CG Distributor. You can see above the CG a perforated plate and a high capacity HEPA filter

Is not conceive a large grade A room (EU GMP laminar flow) without a CG distributor. To supply air to achieve this air velocity means to blow a large amount of air with several fans across HEPA filters. The CG distributor helps air to exit the ceiling at the required velocity.

What is the origin of the CG?


By investigating, I found the US patent 4,023,472 dated from 1977, with the title “APPARATUS FOR PRODUCING A LAMINAR FLOW”. The assignee for this very suggesting title was Ciba-Geigy Corporation. Can you see? Ciba-Geigy, CG.

Ciba Geigy was a former Swiss pharmaceutical company. In 1992 its name was shortened to Ciba, and in 1996, Ciba’s merger with the also Swiss company Sandoz formed Novartis.

You can find the link for this patent here:


The abstract says:

“A laminar flow producing means is described having a blower which passes air to a distributor having a buffer zone with a ratio between its volume and cross-sectional area A being smaller than % VA and two mesh screens spaced about 0.2 to 5 cm apart and each having mesh openings measuring about 0.001 to 1mm so that the air from the blower is passed through the screen meshes seriatim to produce a clean, dust-free laminar flow of air.”

Previously to this invention, the laminar flow could be produced by passing directly from absolute filters. For small areas, like a laminar flow hood, this is not a problem, but for larger areas, like an entire room, it could be very expensive. That means to cover the entire ceiling by HEPA filters!

It was an absolutely revolutionary invention. But you should consider other design aspects for a successfully validated laminar flow room.

Stay tuned for new posts dealing about laminar flow design!

1 Comment
  • Corey Dixon
    Posted at 20:18h, 01 November Reply

    Fantastic article – thank you!

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