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GOST 20568 is a standard specifying how diving masks should be manufactured, tested and distributed within the Union of Soviet Socialist Republics (USSR) and the succeeding Commonwealth of Independent States (CIS). During the latter half of the 1970s, the USSR published Soviet standards GOST 20568 and GOST 22469, dedicated respectively to the diving mask and the swimming fin, which constitute basic underwater diving equipment. Entitled "Маски резиновые для плавания под водой. Общие технические условие" in Russian and subtitled "Rubber masks for submarine swimming. General specifications" in English, GOST 20568 first appeared in 1975 and still applies to rubber diving masks made in Russia and Ukraine (See Figure 1).

Chronology
GOST 20568-75 is the second of the nine known national and international standards on diving masks listed below in order of publication:
 * 1969. British standard BS 4532. Specification for snorkels and face masks. Amended 1977.
 * 1975. USSR/CIS standard GOST 20568. Маски резиновые для плавания под водой. Общие технические условие. Rubber masks for submarine swimming. General specifications.
 * 1980. German standard DIN 7877. Tauch-Zubehör. Tauchbrillen. Sicherheitstechnische Anforderungen und Prüfung. Diving accessories for skin divers. Diver’s masks. Requirements and testing.
 * 1982. Polish Industry Standard BN-82/8444-17.01. Gumowy sprzęt pływacki - Maski pływackie (Rubber swimming equipment - Swim masks).
 * 1985. American national standard ANSI Z87.11:1985. Underwater Safety. Recreational Skin and Scuba Diving. Lenses for Masks.
 * 1988. Austrian standard ÖNORM S 4225. Tauch-Zubehör; Tauchmasken (Tauchbrillen); Sicherheitstechnische Anforderungen, Prüfung, Normkennzeichnung. Diving accessories; divers' masks; safety requirements, testing, marking of conformity.
 * 1989. Chinese national standard CNS 12497. 潛水鏡. Diving mask.
 * 1989. Chinese national standard CNS 12498. 潛水鏡檢驗法. Method of test for diving mask.
 * 2015. European standard EN 16805. Diving equipment. Diving mask. Requirements and test methods.

Typology
Back in 1957, British Sub-Aqua Club co-founder Peter Small counselled: "When looking at a mask, don't be afraid to pull back the lip of the groove that holds the face-plate, to see that it is deep and firm enough to do its job. Where there is a metal band around the outside edge, you won't need this test, but make sure that the band is secure." This advice highlights the difference between two versions of the early diving mask with a single elliptical window. The Typhoon Blue Star mask in Figure 2 illustrates the first kind of mask, which lacks the additional security of a metal rim but can be quickly taken apart for servicing or replacement. The Typhoon Super Star mask in Figure 3 exemplifies the second kind of mask, whose metal rim reinforces the seal between the lens and the rubber body at the expense of easy disassembly and reassembly.

Both these kinds of single-pane masks are broadly representative of the models manufactured in Russia and Ukraine before and after the demise of the USSR. GOST 20568 regulates their production and classifies masks with added lens-retaining rims, bands or clamps as Type I and those without this reinforcement as Type II. By the end of the 1960s, five Type I and five Type II masks were reportedly manufactured in the Soviet Union, while contemporary diving manuals in western countries strongly advocated Type I masks: "Every mask should have a fixing band around the rim of the face plate. The rubber body of the mask is not sufficient to hold the glass in place, and a mask without such a band would tend to leak. Like all diving equipment, the band should be rustproof and, ideally, stainless steel, as this is also strong enough to protect the mask from knocks." Just one Type II and four Type I (see Figure 1) masks remain in production in post-Soviet Russia and Ukraine.

Specifications
Masks must be manufactured in accordance with their accompanying technical specifications, drawings and images. The shape, weight, size and colour must comply with each product's technical description. The Standard relates to the body and the strap of the mask made in any colour of rubber. The physical and mechanical properties of the rubber used in making the masks must must meet certain requirements for tensile strength, elasticity and hardness. The glass used in manufacture must meet certain quality control requirements as well as having smooth edges with no chips or cracks. The mask must be resistant to sea water and any component parts exposed to sodium chloride solution must be free of corrosion. A maximum figure is set for defect tolerance in the body of the mask and in the strap, namely surface bubbles, cavities, ridges, sharp edges and burrs after trimming.

Acceptance rules
Covers quality assurance procedures, including frequency and randomness of product sampling, for evaluating hardness, elasticity and tensile strength. Batches of masks are accompanied by a certificate of quality indicating the manufacturer's name or trade mark, the product's name, the batch number, the number of items in the batch, the date of manufacture and the results of tests confirming compliance with the standard.

Test methods
Visual checks of masks for defects, which are examined with a magnifying glass and measuring instruments. Rubber samples are taken to determine their physical and mechanical properties. Watertightness is tested by pouring water into the mask and placing it on a sheet of paper for 30 minutes to determine whether the paper has any wet spots after this time has elapsed. Weight changes in rubber samples after exposure to sea water are measured.

Marking, packaging, transportation and storage
Masks are to be embossed or labelled with the manufacturer's trademark, the product name, the date of manufacture (quarter, year) and the name of this Standard, while a technical control stamp is to be applied to the rubber masks with indelible ink to mark the date of manufacture. Each mask is to be wrapped in paper or placed in a cellophane or plastic bag and then placed in plywood or wooden boxes which are then tied together with cord or polypropylene strip. A "Warning: fragile!" notice is to affixed. The masks may be carried in any kind of covered vehicle. There are particular rules (specified in other standards) for the transportation of masks to the Far North and other remote areas. Masks should be kept packed in a closed warehouse where the temperature is between 0 and 25ºC at a minimum distance of 1 m from any heat-emitting devices and should not be exposed to sunlight, oil, gasoline, and other substances that deplete rubber and cause corrosion to the metal parts of masks.

Warranty
The manufacturer shall ensure that fins comply with this standard, including the conditions of transportation and storage. The warranty period for rubber masks shall be one year from the date of sale to the retail network, and in the case of non-market consumption, from the customer taking delivery of the product.

Appendix
PACKAGING SCHEMES Wooden or plywood box packaging Image 1—case; 2—band; 3—marking label; 4—pallet Diagram 1

Cardboard box packaging Image 1—carton; 2—polymer film; 3—marking label; 4—pallet Diagram 2