Re: UV lamps and exposure criteria (fwd)

[Radiation Protection <radpro@kaon.mctrf.mb.ca>]

Steve:

I would say that your calculation should be based on the (erythemally) effective 
irradiance and that this shoud be measured, if possible.  Also, I have checked  
my recent copies of the ACGIH TLV booklet and note that they specify a TLV of 
.003 J/cm**2 = 30 J/m**2 rather than the value of 5000 J/m**2 you give.

In addition, if you consider the UV radiation to be composed of only one 
wavelength (313 nm), for which the spectral relative effectiveness (SRE) is .006 
as you note, I would calculate the effective irradiance to be:

     63 W/m**2 x .006 = .38 W/m**2
     
The allowed viewing time (without eye protection) is then:

     30 J/m**2 / .38 W/m**2 = 79 seconds
     
Eric Cowdrey
Department of Medical Physics
Manitoba Cancer foundation 
Winnipeg, Manitoba, CANADA

Tel: 204-787-2166
E-mail: radpro@kaon.mctrf.mb.ca
> Good Afternoon:
> 
> I somehow was bumped off of the listserver and have no gotten back
> on.  I am resending this so there may be some extra stuff at the top
> of the message.  Please excuse this.  Thank you for your help on this
> issue.
> 
> 
> steve at umcp
> hand@wam.umd.edu
> fax: 301-314-9467
> ---------- Forwarded message ----------
> Date: Fri, 21 Mar 1997 14:51:00 -0500 (EST)
> From: steven t hand <hand@wam.umd.edu>
> To: radsafe@romulus.ehs.uiuc.edu
> Subject: UV lamps and exposure criteria
> 
> 	
> 
> I have an experiment involving UV lamps and plants.  I am calculating	
> the irradiance the radiant exposure and trying to deterine allowable
> stay times without eye protection.  Please contact me to let me know
> if my calculations are correct, or where they  are wrong.  Thank you
> very much.
> 
> steve at umcp
> hand@wam.umd.edu
> 
> Wavelength is 313 nm (UV-B range)
> Equation for irradiance from lamp is E=P/2(Pi)rL, where :
> 
> P= 40 Watts/bulb x 12 bulbs
> Pi= 3.14
> r= 1 meter (distance from bulb to researcher)
> L= bulb length = 1.22 meters
> 
> E = 480 Watts / 2*(3.14)*(1m)*(1.22m) = 63 W/m^2
> 
> H the radiant exposure is for an 8 hour exposure 63W/m^2 * 3600 seconds ?
> 
> H = 2.27 x E+5 J/m^2 ?
> 
> 
> or
> 
> Do I calculate the effective irradiance = 63W/m^2 * SRE * wavelength
> 
> E(eff) = 63*(.006)*(313) = 118 W/m^2
> 
> Limiting value for 8 hours from ACGIH TLV is 5000 J/m^2.  Does this imply	
> 
> allowed time t = H/E(eff) = 5000 J/m^2 / 118 W/m^2 = 42 seconds ?
> 
> 
> I am confused about which values to plug in and use, as you can see from
> the above calculations.
> 
> 
> 
> If it is easier to fax me something on this please feel free to do so at
> (301)-314-9467.  Also I can be reached at (301)-405-3985 at work.
> 
> Thanks again.
> 
> 
> ps. standard uvex goggles were purchased at 3.50 for the researchers to
> wear when they were in the room with the lamps.
> 
> 
> 
> 
>