40 CFR 98.207 - Records that must be retained.
(a) Check-out and weigh-in sheets and procedures for gas cylinders.
(b) Accuracy certifications and calibration records for scales including the method or manufacturer's specification used for calibration.
(c) Residual gas amounts (heel) in cylinders sent back to suppliers.
(d) Records, including invoices, for gas purchases, sales, and disbursements for all GHGs.