Laminar flow hood testing - Orchid Board

ericst11 · #1 10-09-2009, 11:17 PM

I Just bought This laminar flow hood from the Nebrsaka university medical center and it says it was checked out in march of 07 and they had just stoped using it when i bought it .The filter looks good . But is there a easy home way to test that it has the right airflow and that the hepa is still good at my home.

Jerry Delaney · #2 10-10-2009, 12:50 AM

Hi Eric,
It's hard to tell from the picture but the hood looks to be in very good condition. Of course, unfortunately, it's physical appearance has nothing to do with the HEPA but well maintained equipment is much less likely to have integrity problems. The best way to check the filter is to have someone DOP test it. However, this requires very expensive equipment and it may be difficult for you to find someone to travel to you home to do the test. A relatively inexpensive way would be for you to expose petri plates containing a sterile nutrient media in various parts of your hood. If you have access to an autoclave (or pressure cooker), you can purchase sterile plastic petri plates and make, sterilize and pour your own plates. A much less frustrating way would be to contact some company like Fisher Scientific, IPM Scientific or any number of others and purchase already made plates of nutrient medium. For your purpose, nutrient agar or TSA agar plates would work fine. If you wish to include a media geared more toward fungi, you might consider the addition of some plates of something like Potato Dextrose Agar or Sabouraud Dextrose Agar. You can purchase packages of 10 plates for ~ $15 + shipping. Just remember when you do the test to turn the hood on and let it run for 15-30 minutes before exposing the plates. It is also a good idea to wipe down the interior surfaces with IPA or bleach solution prior to testing. I have seen plates exposed for 5 minutes in hoods that were in a room undergoing renovation including removal and installation of sheet rock walls that showed 0 contamination. If your exposed plates show no contamination in a period of time that your flasks might be exposed I think you can be assured that the hood's filter is in sufficiently good condition to serve your purpose. Good luck Eric.

ericst11 · #3 10-10-2009, 10:11 AM

Jerry i understand what your saying about the plate process . How about the amout of air coming out of the hood i can barly feel air at the very opening past the glasss is that normal .But i can feel a breeze by the sceen in the back of the hood. How much air flow should there be.

Jerry Delaney · #4 10-10-2009, 10:22 AM

That sounds normal Eric. Another thing you can do is to check the air flow using a "smoke stick". You can find these at most scientific supply houses. Just remember that this will just give you an idea of the air flow and is not an indication of filter integrity. I note I didn't mention it it the previous post but if you do expose some plates, remember to put them in a warm place and incubate them upside down. This will prevent condensate from forming on the agar surface and spreading any small colony that forms.

ericst11 · #5 10-10-2009, 12:33 PM

Jerry i'm testing right now . I had a small tube of agar That a friend gave me from doing some flask for me and i am testing with that . I sterilized with rubbing alcohol and let it run for about 30 min and then sterilized the tube and un caped it hopefully it is contaminit free. By the way i have a minihelic meter it reads at 1.0 is that normal. Thanks Jerry

Jerry Delaney · #6 10-10-2009, 05:27 PM

Quote:

Originally Posted by ericst11

Jerry i'm testing right now . I had a small tube of agar That a friend gave me from doing some flask for me and i am testing with that . I sterilized with rubbing alcohol and let it run for about 30 min and then sterilized the tube and un caped it hopefully it is contaminit free. By the way i have a minihelic meter it reads at 1.0 is that normal. Thanks Jerry

I am unsure just what medium was in the tube. Is it the same medium you used to sow your seed on? If so, I would not necessarily depend upon that medium for filter integrity checks. I would use a good general bacteriological culture media and, as mentioned, another one that is designed for culture of fungi. Also, what is the diameter of the opening on the tube. The most common opening sizes of test tubes are (or used to be) 13, 16, and 25 mm. That size opening is too small to use for testing. Most ready prepared media comes in 100 mm plates thus exposing a much larger surface area.
I don't know what type gauge you have so I can't comment on your reading of 1.0 (and to be truthful, my use of these type gauges happened a lifetime ago). The gauges we used specifically on laminar flow hoods were used to measure the pressure drop across the HEPA. If I remember correctly, a normal reading was usually somewhere between O.25 and 0.50. Higher readings usually meant that the HEPA was ready for replacement (the filters usually lasted 4-6 years with heavy use, but in a clean environment).
If the cost in not prohibitive to you, I think I would still opt to purchase some plates of prepared media as mentioned and proceed from there.