Re: I-131 Air Sampling

[erollins <erollins@conterra.com>]

Keith Varnado wrote:
> 
> At 09:47 AM 6/28/96 -0500, you wrote:
> >
> >     RadSafe,
> >
> >     I am with the Rad. Safety Div. in the Occ. & Env. Safety Office at
> >     Duke Univ.  I am working on a radioiodine (I-131) project looking at
> >     the therapeutic use of I-131 in the hospitals.  One of the aspects of
> >     the project will be air sampling in patient rooms after the patient
> >     has been dosed.
> >
> >     At this point in time I am considering going with a low vol. sampler
> >     (around 2 lpm) using activated charcoal tubes in conjunction with HEPA
> >     filters.  Does this sound like a good idea (or not)?
> >
> >     I would graciously welcome information/advice anyone might have
> >     regarding this type of air sampling (i.e. equipment use, flow rates,
> >     sample times, and any other suggestions)
> >
> >     My e-mail address is brind002@mc.duke.edu
> >
> >     Thanks,
> >
> >     Jim Brindle
> >
> >
> 
> Jim,
> 
> There are several companies that market air samplers, filters,
> supplies, etc.. that will likely assist you. Radeco and F&J
> are two I'm familiar with. My recommendation though would be
> a low volume air sampler which uses a combination filter holder.
> The holder contains a 2" particulate filter and a standard
> activated charcoal cartridge (I would stay away from silver
> zeolite, it's expensive). Use a flow rate of about 2 scfm,
> this gives you a charcoal iodine collection efficiency of
> about 95%. Depending on the form of iodine you will be using,
> you may see activity on the filter paper(I've seen up to 10%
> of of the total iodine activity on the filter paper). Depending
> on the counting system you have, a sampling time of 20-30 minutes
> should get you close to the MDA you are looking for.
> 
> Samplers using carbon vane vacuum pumps are generally low
> maintenance, rugged, and relatively inexpensive. They do make
> noise though. If you attach a short length of tygon tubing to
> the sample holder, you can move the sampler so it will be less
> noisy in the patient room.
> 
> 2 lpm is way too low of a flow for what I think you may want.
> Also, a HEPA filter will not do you much good. If I can provide
> you any more info, let me know.
> 
>         Keith Varnado, CHP
>         kvarnado@premier1.premier.netAlso, beware of problems associated with determination of counting 
efficiency.  We performed extensive bench measurements using I-131 
impregnated charcoal canisters and could not achieve reproducible 
results under laboratory conditions.  This problem is especially 
pronounced when using detectors sensitive to beta particles and low 
energy photons.  NaI detectors seemed to provide the best results under 
field conditions.  

Gene Rollins, CHP