Hello Rohit,
In Risk Assessment you assign agents mainly to support exposure analysis as a method for analysing the risk level and track exposures of employees. Agents carry exposure limits which you compare to measured or
extrapolated exposures at workplaces.
I believe a Exposure analysis is usually not done in the mentioned scenario, since Biological agents are usually not measured, you should use 'no agents' for this Hazard class.
I have searched in many places and haven't found any evidence that this configuration can be adapted.
Also don't think that makes sense to 'measure' a Biogical Risk and compare it with threshold limits.
Best regards,
Raphael