Division 2.2.1.(c) — 1. Subparagraph 1 (c) — Ventilation apertures

Their greatest dimension must, in principle, not exceed 400 mm.

Apertures permitting direct access to the load compartment, must be obstructed by means of wire gauze or perforated metal screens (maximum dimension of holes: 3 mm in both cases) and protected by welded metal lattice work (maximum dimension of holes: 10 mm).

Apertures not permitting direct access to the load compartment (e.g. because of elbow or baffle-plate systems) must be provided with the same devices, in which, however, the dimensions of the holes may be as much as 10 and 20 mm respectively.

Where openings are made in sheets, the devices referred to in subparagraph (b) of this note must in principle be prescribed. However, blocking devices in the form of a perforated metal screen fitted outside, and wire or other gauze fitted inside, will be allowed.

Identical non-metal devices may be allowed provided that the holes are of the requisite dimensions and the material used is strong enough to prevent the holes from being substantially enlarged without visible damage. In addition, it must be impossible to replace the ventilation device by working from one side of the sheet only.