TM 5-4220-225-14 Table 2-1.  Operator Preventive Maintenance Checks and Services (Cont). B - Before D - During A - After Q - Quarterly Interval Item Item to be Inspected. Equipment Will Be No. B D A Q Procedure Reported Not Ready If HELMET ASSEMBLY (Cont) b.  Inspect the supply valve assembly for corrosion Inspection reveals any of the and damage.  Ensure the valve mounting and defects sighted above or packing gland nuts are snug. any defect that renders the helmet inoperable. 10. Air Supply Diffuser. Inspect for dirt, oil, moisture, and corrosion.  Replace Inspection reveals any of the filter elements (felts) if required. defects sighted above or any defect that renders the helmet inoperable. 11. Exhaust Valve Assembly. Inspect for dirt, corrosion, deteriorated rubber parts, Inspection reveals any of the and loose or missing screws.  Replace parts as defects sighted above or necessary. any defect that renders the helmet inoperable. 12 Helmet Communication System. a.  Inspect the communication whip assembly for corrosion, damage, and deterioration. b.  Inspect the helmet wiring for broken or shorted leads, corroded terminals, and damaged insulation. c.  Inspect the earphones and microphone for Inspection reveals any of the physical damage, dirt, corrosion, moisture, defects sighted above or punctured moisture barriers, loose connection, any defect that renders the and loose mounts or retainers. helmet inoperable. d.  Perform a communications test (para.  2-8e) Helmet fails test. 2-8