UNIWELD 40040 NITROGEN SLUDGE SUCKER/BLASTER KIT (RHP400, 516 STAND) UPC 40040 NEW The preferred gas for the Sludge Sucker is Nitrogen because it's a dry gas that has multiple uses: purging an A/C&R system, leak testing a refrigerant line, calibrating pressure controls, cleaning a condensate drain line, cleaning coils, inflating tires, new