Venting pits, and the value of

There was a recent query about the requirements of AS 2885.1 for venting below-ground structures such as valve pits. It turns out the Standard is incomplete, because an editorial change in 1997 inadvertently omitted a key sentence and no-one noticed until 25 years later. Subsequent revisions of the Standard had applied the “ain’t broke, don’t fix it” principle and failed to notice the broken bit.

On the one hand the fact that no-one noticed could be interpreted as meaning that the relevant clause is in fact not very relevant at all. On the other hand, just because a requirement is not referred to very often doesn’t mean the Standard should ignore it. If and when you are designing a large below-ground pipeline structure the sealing or ventilation of it could be critically important to safety. In any case, others have possibly noticed the anomaly but had no easy way of raising the issue to get it fixed. provides an avenue for any user of the Standard to raise issues such as this.

So what was the problem? Clause 6.5.3 of AS 2885.1-2018 specifies that below-ground structures of less than 6 m3 volume may be sealed or vented, but is silent on larger structures. It turns out that AS 2885-1987 (note the year!) included a sentence that “Any other structure shall be ventilated.” (i.e. must not be sealed). However that sentence was lost from all subsequent revisions. More detail here.

The take-home message is that no matter how hard committees try to get AS 2885 exactly right there are things that slip through, but if you find anything that you think is incomplete, wrong, ambiguous, etc then send an email to And if you have to design a big pit, make sure it is ventilated in accordance with Part 1 Clause 6.5.2(d).

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