Well I didn't think it needed that much detail, but hey
The US1/DS1 was orginally designed for ponies & commercial work with one LP & 1 HP port at a time when it was
common to use adapters on first stages to add LP ports. Since then the use has expanded as diving changed and
with many already in divers possesion got repurposed for suit inflate. These are a simple LP hose going direct to a
drysuit inlet and is still a fairly common rig. .
Nowdays and with the systems being used a lot more, especially in the tec realm a over pressure relief valve in
some circles is reccommended. Those already with a DS1 and a handy adapter, for the cost of about £25 a OPRV
can be added. For those buying new or S/h not a lot of point as the DS4 is more plentiful anyway and negates
the need for the adapter.
Is it wrong or a bad idea NOT to have a OPRV? Comes down to the old assessment of what is a very low risk and
how often this is likely to happen if at all, how catastrophic and even then how effective any protocols that are in
place to deal with it. Old school tend to be happy, the young turks not so much, so you takes your choice