Right, on to the second item of diving headgear. I shall dedicate this thread to three Standards (British, German and European) with specifications for snorkels, attempting once again to determine what they all have in common and what sets each of them apart. In this first message of the thread I return to British Standard 4532:
1. British Standards Institution (December 1969) BS 4532. Specification for snorkels and face masks. London: British Standards Institution. This British Standard, which was amended on 30 December 1977 and whose status remains "current", is 11 pages in length and available for purchase from http://shop.bsigroup.com/ProductDetail/ ... 0000132783
Foreword: According to this section preceding the specification proper, "a snorkel allows (the wearer) to breathe without having to raise the mouth out of the water whilst swimming, or floating face downward with nose and mouth submerged." Snorkels used both by the "untrained or casual skin diver" and by the "fully equipped free diver" are covered.
Scope: The Standard specifies requirements for "snorkels (...) used for recreational purposes."
General: This section defines and dimensions the snorkel:
Materials and design: This section elaborates on what is written in the preceding section, specifying the characteristics of the mouthpiece orifice and lugs, the tube, the mask attachment loop and any shut-off valve fitted. Tubes with an internal diameter greater than 20 mm are declared unsuitable for children:
Instructions: The Standard requires a warning label to be affixed to the tubes of all snorkels and a set of instructions to be enclosed with each snorkel. I have posted below the BS4532-prescribed "safety notes" enclosed with a Britmarine snorkel I have in my collection, made by the former underwater gear manufacturer Haffenden-Richborough of Sandwich in Kent in the south-east of England:
Marking: The Standard requires compliant snorkels to be marked with this British Standard's number and the manufacturer's name. Snorkels whose internal dimensions rendered them unsuitable for children had to be marked accordingly:
Appendices: Appendix A describes a "test for rigidity of tube":
So those are the implications of BS4532:1969 for snorkels. I'll finish with a scan of the snorkels page from a 1970s Haffenden-Richborough underwater catalogue referring to BS4532 compliance:
In case the BS4532-related wording on the page isn't clear, here's a blow-up:
Can you work out why the snorkel with the designation B.33 Mariner is non-compliant? It's because it has a soft, flexible, corrugated portion between the mouthpiece and the tube proper, allowing the mouthpiece to hang down vertically and out of the way when the snorkel is not in use. Such an arrangement would cause the snorkel to fail the snorkel rigidity test when applied to the "curve of the tube". Such "concertina" snorkel designs are much rarer nowadays, but there is still one around, the "Seac Corrugated Old Style Snorkel":
However, the snorkel's mouthpiece and collapsible corrugated bend are both made from EPDM rather than natural rubber.
I hope this posting has been of some interest. In my next posting to this thread I shall be taking a look at the German Standard for snorkels, DIN7878 of February 1980.