With Bryan's encouragement, I am now moving from footgear to headgear. I shall dedicate this thread to three National Standards (British, German and Russian) with specifications for diving masks, attempting once again to determine what they all have in common and what sets each of them apart.
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BS4532:1969 specifies requirements for snorkels as well as diving masks. Here, however, I shall focus on what the normative document has to say about masks, leaving my exploration of National Standards for snorkels to a separate future thread.
Foreword: According to the this section preceding the specification proper, "a face mask enables the wearer to see underwater and prevents water from being breathed up the nose inadvertently." Masks used both by the "untrained or casual skin diver" and by the "fully equipped free diver" are covered.
Scope: The Standard specifies requirements for "face masks used for recreational purposes."
General: Mask consists of "a piece of transparent material sealed to the face in a watertight manner." Drain valves/compensators are not essential, while combined masks and snorkels are not acceptable.
Materials and design: Prescribes first that the mask skirt should be flexible enough to provide "good sealing efficiency and comfort" but not so flexible as to allow the mask to "collapse during inhalation underwater." Proceeds to prescribe mask dimensions:
There follows a list of requirements for the toughened glass or plastic "eyescreen", the "retaining rim" and the "circumferential clamp", all providing "watertightness." A split headstrap with a non-slip buckles is prescribed. Any drain valve is to be fitted in the lowest point, permitting removal for cleaning purposes and preventing water from entering.
Fit of face masks: Explains how mask fit is gauged by trying on a mask without using the headstrap then inhaling through the nose to retain the mask in position without other support.
Instructions: The Standard requires a warning label to be affixed to eyescreens and a set of instructions to be enclosed with all masks. I have posted below the BS4532-prescribed "safety notes" enclosed with a Britmarine mask 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 masks to be marked with this British Standard's number and the manufacturer's name.
Appendices: Appendix B describes two mask watertightness tests. The first involves supporting the mask, face downwards, over a sheet of blotting paper, filling the cavity with ink-stained water and examining the outer eyescreen and blotting paper for signs of ink after one hour has elapsed. The second test involves placing the mask, face downwards, in an empty bowl, weighting the mask down, pouring water into the bowl and examining the inside of the mask after one hour for signs of water ingress from the bowl.
So that's the lowdown on BS4532:1969. I'll finish with a scan of the diving masks 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:
I hope this posting has been of some interest. In my next posting to this thread I shall take a look at the German Standard for diving masks, DIN7878 of November 1980.
1. British Standards Institution (December 1969) BS 4532. Specification for snorkels and face masks. London: British Standards Institution. This British Standard, whose status remains "current", is 11 pages in length and available for purchase from