DCM8: Heat complete. Upon arrival David Lester said they recently expanded and wanted us to check the two units in that building as well as the original 6. All 8 systems have compromised heat exchangers, meaning there is a greater risk for carbon monoxide to get into the building and/or cause systems to shut off due to cracks in the heat exchangers. Original 6 systems are approximately 26 years old and 2 systems in new building are 25 years old. Put compromised heat exchanger stickers on all units and informed David of issue. Left systems 1-7 running due to water pipes, sprinkler heads and product all being in the conditioned space. If we turn off units the water pipes could potentially freeze, cracking and then spilling water into warehouse. Set all thermostats to 50*. System 8 is not functioning the igniter control board has failed and system will not heat without igniter. Heat exchanger is compromised. Turned gas off to unit. Comfort advisor will need to give a quote for replacing