Air lock to prevent Flow of Contaminants
Air lock to prevent Flow of Contaminants
(OP)
In my current project, I have to prevent transfer of contaminants from antibiotic lab to the production area. The antibiotic lab and storage / production area is seperated by a link bridge. Though antibiotic area is kept at negative pressure with respect to the link bridge but it is still considered as sterile area and we need to wear protective clothing to enter in the lab. In all cases, the contaminatns are not allowed to enter into the lab through production / storage area and vice versa but conveyer will pass through the lab to the warehouse area through a link bridge and there will be opening between between the lab and the link bridge.
To prevent the contaminats to flow in either direction, I have now decided to provide an air lock in the link bridge with duty /standby exhaust fan on the roof of the link bridge.The exuasut fan will exhaust air from the air lock and hence it create an air lock between the lab and warehouse / production areas. I would like to know the following.
1. Is there any other better strategy to prevent the contaminatns to flow from production area / warehouse to the lab and vice versa.
2.The suitable type of exhaust fan to be selected.
3. How much exhaust air to be exhausted from the air lock to create an proper air lock to prevent the contamination flow in either direction.
To prevent the contaminats to flow in either direction, I have now decided to provide an air lock in the link bridge with duty /standby exhaust fan on the roof of the link bridge.The exuasut fan will exhaust air from the air lock and hence it create an air lock between the lab and warehouse / production areas. I would like to know the following.
1. Is there any other better strategy to prevent the contaminatns to flow from production area / warehouse to the lab and vice versa.
2.The suitable type of exhaust fan to be selected.
3. How much exhaust air to be exhausted from the air lock to create an proper air lock to prevent the contamination flow in either direction.





RE: Air lock to prevent Flow of Contaminants
If you maintain 150 fpm through both the openings, you can restrict contamination. You may need to go for HEPA in the exhaust if your antibiotic lab is negative with respect to airlock.
RE: Air lock to prevent Flow of Contaminants
B.E.
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RE: Air lock to prevent Flow of Contaminants
You understood it correctly. I have attached sketch for your further review advise. Can I have any reference for maintaining 150 fpm through both the conveyor openings for restricting the contaminants. I think hepa filter is not required for exhausting air from an antibiotic to outside as it is not so hazardous. The peoples are already working in the lab without any special precaution such as mask.
RE: Air lock to prevent Flow of Contaminants
I'm no expert in sterilization of airstreams, maybe there are more suitable products. Electrostatic etc.
I agree with quarks comment that maintaining a velocity through the openings is a solid approach. Think about it from a pressure perspective. if you need to maintain say 0.05" SP across the openings, then work out the free area and pressure drop. You also have to figure in the area of the one of the doors into your airflow rate - you may need to control the fan based on differential pressure.
RE: Air lock to prevent Flow of Contaminants
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RE: Air lock to prevent Flow of Contaminants
Bio safety cabinets and fumehoods are operated with 0.5 m/s open sash velocity, to minimize operator exposure. Isolator glove breach velocity is about 0.7 to 0.75 m/s. These are established values by surrogate testing. Another point is, Munter recommends 150 fpm velocity across openings to minimise water vapour diffusion.
As you mentioned that the lab is sterile one, I presume it to be of Class B. Conveyor movement generates lot of particles. You should be careful.
RE: Air lock to prevent Flow of Contaminants
RE: Air lock to prevent Flow of Contaminants
Noted with thanks.
RE: Air lock to prevent Flow of Contaminants
3.26 ft x 2.65 ft = 8.63 ft² = 0.801 m². As per client, -4 pa to be maintained in the air lock.
The required air will be exhasuted from the air lock to create -4pa differential pressure between the air lock and the link bridge as per equation Q = 2610 x A x (DP)1/2 and the equvalent amount of pre-cooldedfresh air will be provided in the link bridge.
Since antibiotic lab is already negatively pressurized with respect to the link bridge, it was assumed that air will only be drawn into the air lock through the conveyor opening between the link bridge and the air lock.
Based on calculations, the required air flow to be exhasuted from an air lock is 3100 cfm and equivalent amount of pre-cooled fresh air to be provided in the link bridge.
Appreciate, if anybody can provide valuable input on this.
RE: Air lock to prevent Flow of Contaminants
This air could come from your lab ventilation system
RE: Air lock to prevent Flow of Contaminants
RE: Air lock to prevent Flow of Contaminants
Similar topics have been discussed before: http://www.eng-tips.com/viewthread.cfm?qid=43928 (this thread also references older threads)
RE: Air lock to prevent Flow of Contaminants