Optimizing Airflow for Positive Pressure Box Design

In summary, the speaker is seeking help in creating a box with positive pressure to keep out dust and lint while working on a project. They have a question about the required airflow for an 18"x5" opening and are considering using a fabric shroud over the opening to minimize the flow needed. They are looking for clarification and have been researching this topic but have not been able to find a solution.
  • #1
StanknRankin
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I am not an engineer which is why I have come to this forum.

I am currently working on a project for my business. I am trying to create a box that needs positive pressure. My basic requirements are to keep out dust and lint from contaminating my work.

There will be an opening on this box where the air will be leaving the chamber. This is the same opening that your hands will go through(I understand that my hands can contaminate the environment etc...). Talking with a friend I am under the impression that to create an environment with positive pressure the only factor I need to figure is the size of the opening. The volume of the chamber does not matter.

My question is as follows. If my opening is 90 inches square(18x5"), how much filtered airflow is required? I know there is a measurement involving CFM which is cubic feet per minute. I have another friend who says I should use about 150 CFM. I don't think this is right because that rating doesn't associate with the opening. And 90 inches squared has no value of time.

Can someone please break this down for me? I have been on google for a long time and I can't seem to figure this out.

Thank you in advance!

Kevin
 
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  • #2
I presume you look through a transparent window. The airflow must be sufficient to prevent air currents bringing external air back in through the hand hole. You can minimise the flow required by attaching a lint-free fabric shroud over the 18”x5” aperture, with fabric tubes attached for your arms and hands to pass through. Whatever pressure you have will then bleed between the shroud and your arms. The better that fit, the less the flow required. At this point you should experiment with a shroud and a small fan.
 

1. What is positive pressure and why is it important in a laboratory setting?

Positive pressure is a condition in which the pressure inside a closed system or room is greater than the pressure outside. In a laboratory, positive pressure helps to prevent the entry of outside contaminants, such as dust or bacteria, which can compromise experiments or samples. It also helps to maintain a clean and sterile environment for sensitive experiments.

2. How is positive pressure created in a laboratory?

Positive pressure is typically created using an air supply system, such as an air handler or a cleanroom air filtration unit. These systems introduce filtered air into the laboratory, creating a higher pressure inside compared to the outside. Some laboratories may also use air locks or positive pressure chambers to further control and maintain positive pressure conditions.

3. What are the potential risks of not having positive pressure in a laboratory?

Without positive pressure, a laboratory is vulnerable to outside contaminants, which can compromise experiments and samples. This can lead to inaccurate results and potential safety hazards. In addition, without positive pressure, air can flow out of the laboratory, carrying potentially hazardous substances with it, posing a risk to the surrounding environment and individuals.

4. How can positive pressure be maintained in a laboratory?

In order to maintain positive pressure, it is important to regularly monitor and maintain the air supply system and any additional equipment, such as air locks or chambers. This includes regularly changing filters and ensuring that all equipment is functioning properly. It is also important to minimize the number of doors and windows in the laboratory and to keep them closed as much as possible to prevent air from escaping.

5. Are there any potential downsides to using positive pressure in a laboratory?

One potential downside of using positive pressure in a laboratory is the cost associated with installing and maintaining the necessary equipment. In addition, positive pressure can make it more difficult to control temperature and humidity levels, which may be important for certain experiments. It is important to carefully consider the specific needs of a laboratory before implementing positive pressure measures.

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