At 15:31 (07:31) received low pressure alarm on PT-199 Instrument Air. Cheryl trended the channel and found the pressure dropping rapidly; passing through 50PSIG. 

   I called Kyle. He gave me instructions on running the compressor by hand. Went to Chiller Yard and turned on both compressors by hand. Both worked in the Hand position but did not run in the Auto position. Switched compressor #1 to Hand and built pressure up to  95PSIG. Put switch back into the Auto position. 

  As of 15:52 (07:52) Kyle was on site looking into the problem.