What is the procedure for in-place test?

Actually, it is rather simple. A DOP generator introduces aerosol as a challenge agent into the upstream side fo the filter system. A sample of this aerosol-air mixture is taken on the upstream side of the filter with a linear forward light scattering photometer for use as a baseline to compare the downstream readings. since the upstream concentration is known, and the photometer is linear, the downstream samples may be read out in percent of concentration, as recommended in the standards and specifications. Any leak greater than 0.01% of the upstream concentration is too much, and the spot should be marked for repairs in actuality, there should be no leaks around the filter seals, and in practice, readings at the face of the filter are usually in the 0.004% to 0.008% range.