✓ denotes a primary measurement, (S) denotes a supporting measurement, (SUR) denotes a surrogate gas used for validation of instrument performance, which may or may not be useful for a customer’s measurement purposes, depending on precision requirements. All instruments measure water for correction purposes.

✓ denotes a primary measurement, (S) denotes a supporting measurement, which may or may not be useful for a customer’s measurement purposes, depending on precision requirements. All instruments measure water for correction purposes.