---
kind: "section"
citation: "33 C.F.R. § 183.630"
title: "33"
number: "183.630"
heading: "Standards for natural ventilation."
url: "https://uscodex.org/cfr/33/183.630"
---

# §183.630. Standards for natural ventilation.

- (a) For the purpose of [§ 183.620](/cfr/33/183.620.md), “natural ventilation” means an airflow in a compartment in a boat achieved by having:
  - (1) A supply opening or duct from the atmosphere or from a ventilated compartment or from a compartment that is open to the atmosphere; and
  - (2) **An exhaust opening into another ventilated compartment or an exhaust duct to the atmosphere.**
- (b) Each exhaust opening or exhaust duct must originate in the lower third of the compartment.
- (c) Each supply opening or supply duct and each exhaust opening or exhaust duct in a compartment must be above the normal accumulation of bilge water.
- (d) Except as provided in [paragraph (e)](#e) of this section, supply openings or supply ducts and exhaust openings or exhaust ducts must each have a minimum aggregate internal cross-sectional area calculated as follows:
  - (1) A is the minimum aggregate internal cross-sectional area of the openings or ducts in square inches;
  - (2) V is the net compartment volume in cubic feet, including the net volume of other compartments connected by openings that exceed 2 percent of the area between the compartments; and
  - (3) ln (V/5) is the natural logarithm of the quantity (V/5).
- (e) The minimum internal cross-sectional area of each supply opening or duct and exhaust opening or duct must exceed 3.0 square inches.
- (f) The minimum internal cross-sectional area of terminal fittings for flexible ventilation ducts installed to meet the requirements of [paragraph (d)](#d) of this section must not be less than 80 percent of the required internal cross-sectional area of the flexible ventilation duct.

## Notes

### Amendments

[CGD 76-082, 44 FR 73027, Dec. 17, 1979; 45 FR 7544, Feb. 4, 1980]

### Source

Source: CGD 76-082, 44 FR 73027, Dec. 17, 1979, unless otherwise noted.

### Authority

Authority: 46 U.S.C. 4302; Pub. L. 103-206, 107 Stat. 2439; and Department of Homeland Security Delegation No. 0170.1, para. II, (92)(b). Subpart E is also authorized by Pub. L. 114-120, 130 Stat. 27

### Source

Source: CGD 72-61R, 37 FR 15782, Aug. 4, 1972, unless otherwise noted.

### Amendments

[CGD 76-082, 44 FR 73027, Dec. 17, 1979; 45 FR 7544, Feb. 4, 1980]