Sampling Facility (Room) for Potent Compounds

Just wanted to know opinions -
For potent compounds sampling from bulk containers, if one decides to build a separate room, what should be the pressurization of that room? Positive to the outside area or negative to outside area? The outside area is a Warehouse which has HVAC supplied air. The room does not have separate AHU, but has fan powered HEPA filters to supply air. Moreover, sampling will be performed under Ventilated Balance System (Negative air pressure to the room).
Following situations need to be taken into consideration -

  1. Room is positive to the warehouse - If the material spills inside the room, the air will carry it into warehouse area.
  2. Room is negative to the warehouse - If there is no anti room (material air lock) the room will pull dirty air from the warehouse.
  3. Room has two air locks, one for personnel and one for material transfer. The room is negative to both airlocks (airlocks are bubble out) - In case of spillage, the air inside the room remains inside the room

Here is a good reference.

http://apps.who.int/prequal/info_general/documents/TRS961/TRS961_Annex5.pdf

I think you are correct. Negative pressure (sink) can contaminated the product. Positive pressure (bubble) can contaminated the environment with product.

So you have a few scenarios

  1. Control the room pressure compared to the warehouse
  2. Control the room pressure vs the air lock vs. the warehouse.

One option is to make the airlock negative to the warehouse, and also make the airlock negative to the sampling room. Contamination from the warehouse will be left in the negative pressure airlock. Product from the sampling room will be left in the negative pressure airlock. This will satisfy both criteria.

NOTE: That there is another scenario. For sterile powder filling (which is the most difficult, for containment and sterile reasons, but which might be most similar to your process) people often use double airlock design. This pressure goes warehouse - airlock - airlock - room. Where airlock is β€œ0” (warehouse) to β€œ-” (airlock) to β€œ0” (airlock) to β€œ+” (room). That way the room is positive to the warehouse, but there is an airlock which traps all the product before it gets into the warehouse.

In the guildelines EU and WHO (I think) a pressure cascade of 10 Pa is targeted with a range of 5-15 Pa is possible for each β€œstep”. This equates to 2-7 inches of water per β€œstep”.

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