---
kind: "section"
citation: "40 C.F.R. § 1065.325"
title: "40"
number: "1065.325"
heading: "Intake-flow calibration."
url: "https://uscodex.org/cfr/40/1065.325"
---

# §1065.325. Intake-flow calibration.

- (a) **Calibrate intake-air flow meters upon initial installation.** Follow the instrument manufacturer's instructions and use good engineering judgment to repeat the calibration. We recommend using a calibration subsonic venturi, ultrasonic flow meter or laminar flow element. We recommend using calibration reference quantities that are NIST-traceable within ±0.5% uncertainty.
- (b) You may remove system components for off-site calibration. When installing a flow meter with an off-site calibration, we recommend that you consider the effects of the tubing configuration upstream and downstream of the flow meter. We recommend specifying calibration reference quantities that are NIST-traceable within ±0.5% uncertainty.
- (c) If you use a subsonic venturi or ultrasonic flow meter for intake flow measurement, we recommend that you calibrate it as described in [§ 1065.340](/cfr/40/1065.340.md).

## Notes

### Amendments

[70 FR 40516, July 13, 2005, as amended at 88 FR 4675, Jan. 24, 2023]

### Authority

Authority: 42 U.S.C. 7401-7671q.

### Source

Source: 70 FR 40516, July 13, 2005, unless otherwise noted.

### Amendments

[70 FR 40516, July 13, 2005, as amended at 88 FR 4675, Jan. 24, 2023]