sn2021

sn2021, Total:200 items.

The international standard classification for "sn2021" includes: .

The Chinese standard classification for "sn2021" includes: .

Professional Standard - Commodity Inspection

SN/T 5405.5-2021 Technical guide to certification in the internet environment Part 5: Review and attestation
SN/T 5364.8-2021 Droplet digital PCR method for detection of pathogens in exportfood - Part 8: Cronobacier spp. (Enterobacter sakaz.akii)
SN/T 5321-2021 Determination of aldehydes and ketones in footwear - High performance liquid chromatography
SN/T 5364.4-2021 Droplet digital PCR method for detection of pathogens in export food - Part 4: Vibrio vulni ficus
SN/T 5406-2021 Detection of genetically modified components in edible vegetable oil for import
SN/T 5302-2021 Rules for inspection of steel for the reinforcement of concrete for import
SN/T 5313.4-2021 Specificaion for business and technical inspection of import and export commodity inspection and appraisal institutions-Part 4:Weight survey by weighing instrument
SN/T 1795.2-2021 Rules for inspection of used mechanical and electronic products for import - Part 2: Pre-shipment inspection
SN/T 5208-2021 Detection and Identification of Pratylenchus spp. (non-Chinese species) Filipjev,1936
SN/T 2419.2-2021 Rules for inspection of furniture for import - Part 2: Children furniture
SN/T 5337-2021 Quarantine protocol for species identification for tick vectors transmitting animal diseases
SN/T 4246.3-2021 Rules for the inspection of imported mechanical and electric equipment for maintenance - Part 3: Enterprise maintenance capability assessment requirements
SN/T 5176-2021 Rapid test codes for infectious disease at frontier port
SN/T 5290-2021 The method of quantitative analysis for import and export feather &down and polyester fibers blended textile by using hypochlorite
SN/T 5364.3-2021 Droplet digital PCR method for detection of pathogens in exportfood - Part 3 Vibrio alginolyticus
SN/T 5317-2021 Determination of organophosphorous flame retardants in import and exportleather and its products-Gas chromatography-mass spectrometry method
SN/T 4037-2021 Rules for the inspection of wood products for import
SN/T 4763.2-2021 Determination of mercury in coal-Oxygen bomb combustion-Atomic fluorescence spectrometric method
SN/T 5311-2021 Determination of hydrogen sulfide in crude oil and fuel oils - Rapid liquid phase extraction method
SN/T 5344-2021 Down and feather for import and export - Determination of oil and fat content - Accelerated solvent extraction method
SN/T 5172-2021 Vector density control level at food manufactory of frontier ports
SN/T 5364.2-2021 Droplet digital PCR method for detection of pathogens in export food - Part 2: Vibrio cholerae
SN/T 5296-2021 Construction and configuration guide for negative pressure quarantine isolation facilities at port
SN/T 5298-2021 Rules for the inspection of crude glycerin for import
SN/T 5361-2021 Detection of Cronobacter sakazakii in export food fusA gene sequencing method
SN/T 4233-2021 Construction standards for designated quarantine facilities for importedcattle/sheep/goats
SN/T 5299-2021 Rules for the inspection of compounded rubber for import
SN/T 5175-2021 ldentification codes for mosquitos with DNA barcoding at frontier ports
SN/T 5354.1-2021 Test methods for anti-skid properties of floor materials Part 1: Pendulum method
SN/T 5322-2021 Identification of regenerated leather
SN/T 0947-2021 Inspection rule for import children's footwear
SN/T 5355-2021 Test method for anti-slip performance of ceramic floor tiles - dynamic friction coefficient method
SN/T 5386-2021 Detection and identification of Gra pevine Pinot gris virus
SN/T 5382-2021 ldentification of Cibotium barometz (L.) J. Sm.
SN/T 5315-2021 Test method of photocatalytic ceramics for self-cleaning - Fluorescence probe method
SN/T 5291-2021 Specification for construction of Customs radioassay laboratories
SN/T 5372.2-2021 Technical specifications of health quarantine laboratory testing on entry-exit special goods - Part 2: Sampling and delivering rules
SN/T 5357-2021 Determination of multi-groups of illegal additives in health foods for export-LC-MS/MS Method
SN/T 5295-2021 Guidelines for basic statistics in chemical analysis laboratories
SN/T 5323-2021 Food contact material Polymers Determination of p-hydroxy-benzoate estersmigrated from plastics - Liquid chromatography tandem mass spectrometry
SN/T 5405.2-2021 Technical guide to certification in the internet environment Part 2: Establishment of evaluation index
SN/T 5318-2021 Determination of polycyclic aromatic hydrocarbons in tyres-Nuclear magnetic resonance method
SN/T 5310-2021 Determination of p-t-amylphenol and p-t-octylphenol in coatings - Gas chromatography
SN/T 5364.7-2021 Droplet digital PCR method for detection of pathogens in export food - Part 7: Shiga Toxin-producing Escherichia coli
SN/T 5312-2021 General requirements for inspection of imported cores forremanufacturing mechanical components & parts in free trade zon
SN/T 5371-2021 Detection method of schistosoma by PCR and real-time fluorescence PCR at frontier ports
SN/T 5314-2021 Rules for application of unmanned aircraft on draft survey
SN/T 5313.1-2021 Specification for-business and technical inspection of import and export commodity inspection and appraisal institutions- Part 1: General rules
SN/T 5359-2021 Determination of azithromycin residue in foodstuffs of animal origin for export-LC-MS/MS method
SN/T 5352-2021 Determination of perfluorinated and polyfluorinated compounds in paper heat-resisting material
SN/T 4675.32-2021 Method for the determination of nitrogen stable isotope ratio in wine for export
SN/T 5356-2021 Test method for surface wear resistance of sanitary ware
SN/T 2021-2007 Protocol of quarantine for bovine anaplasmosis
SN/T 5177-2021 Real-time RT-PCR method for detecting Zika Virus at frontier ports
SN/T 5353-2021 Rules for the inspection of imported recycling iron-steel materials
SN/T 5300-2021 Guide of customs technical specifications - SN professional standard for entry-exit inspection and quarantine
SN/T 5343-2021 Functional inspection on water resistance and water vapour permeability of textiles for import and export
SN/T 5297-2021 Determination of hexabromocyclododecane in polymers for electricaland electronic products -Qualitative screening by pyrolysis gas chromatography-mass spectrometry
SN/T 2032-2021 Construction standards for designated quarantine facilities for imported breeding swine
SN/T 5348-2021 Determination of contents in industrial nonyl alcohol - Gas chromatography
SN/T 5309-2021 Food contact materials Polymers Determination of nonylphenol and octylphenol in food simulants Liquid chromatography-mass spectrometry method
SN/T 5307-2021 Petroleum products-Determination of fluorine, chlorine and sulfur content - Direct combustion-ion chromatography
SN/T 2419.1-2021 Rules for the inspection of furniture for import Part 1: General furniture
SN/T 5173-2021 Real-time RT-PCR method for detecting Heartland Virus in ticks at frontier ports
SN/T 4624.20-2021 Test method of import microbe agentia in the environment protection - Part 20: Paracoccus pantotrophus

Swiss Association for Standardization (SNV)

SN ISO 9523:2021 Touring ski-boots for adults - Interface with touring ski-bindings - Requirements and test methods
SN ISO 37000:2021 Governance of organizations — Guidance
SN ISO 9838:2021 Alpine and touring ski-bindings - Test soles for ski-binding tests
SN ISO 10002:2021 Quality management - Customer satisfaction - Guidelines for complaints handling in organizations
SN ISO 15177:2021 Hot-rolled twin-roll cast steel sheet of commercial quality
SN ISO 24016:2021 Jewellery and precious metals - Grading polished diamonds - Terminology, classification and test methods
SN EN ISO 21392:2021 Cosmetics - Analytical methods - Measurement of traces of heavy metals in cosmetic finished products using ICP/MS technique (ISO 21392:2021)
SN EN ISO 12404:2021 Soil and waste - Guidance on the selection and application of screening methods (ISO 12404:2021)
SN EN ISO 11755:2021 Gas cylinders - Cylinder bundles for compressed and liquefied gases (excluding acetylene) - Inspection at time of filling (ISO 11755:2005)
SN EN 17035-2021 Surface active agents - Bio-based surfactants - Requirements and test methods
SN EN ISO 21676:2021 Water quality - Determination of the dissolved fraction of selected active pharmaceutical ingredients, transformation products and other organic substances in water and treated waste water - Method using high performance liquid chromatography and mass spe
SN EN ISO 11132:2021 Sensory analysis - Methodology - Guidelines for the measurement of the performance of a quantitative descriptive sensory panel (ISO 11132:2021)
SN EN ISO 19957:2021 Footwear - Test methods for heels - Heel pin holding strength (ISO 19957:2021)
SN EN ISO 22818:2021 Textiles - Determination of short-chain chlorinated paraffins (SCCP) and middle-chain chlorinated paraffins (MCCP) in textile products out of different matrices by use of gas chromatography negative ion chemical ionization mass spectrometry (GC-NCI-MS) (I
SN EN ISO 16186:2021 Footwear - Critical substances potentially present in footwear and footwear components - Determination of dimethyl fumarat (DMFU) (ISO 16186:2021)
SN EN ISO 23903:2021 Health Informatics - Interoperability and integration reference architecture - Model and framework (ISO 23903:2021, Corrected version 2021-07)
SN EN ISO 24267:2021 Footwear - Determination of coefficient of friction for footwear and sole components - Test method (ISO 24267:2020)
SN EN 17477-2021 Algae and algae products - Identification of the biomass of microalgae, macroalgae, cyanobacteria and Labyrinthulomycetes - Detection and identification with morphological and/or molecular methods
SN EN 17285-2021 Railway applications - Acoustics - Measuring of door audible warnings
SN EN ISO 10873:2021 Dentistry - Denture adhesives (ISO 10873:2021)
SN EN ISO 27509:2021 Petroleum and natural gas industries - Compact flanged connections with IX seal ring (ISO 27509:2020)
SN EN ISO 20475:2021 Gas cylinders - Cylinder bundles - Periodic inspection and testing (ISO 20475:2018)
SN EN 13623-2021 Chemical disinfectants and antiseptics - Quantitative suspension test for the evaluation of bactericidal activity against Legionella of chemical disinfectants for aqueous systems - Test method and requirements (phase 2, step 1)
SN EN ISO 7541:2021 Spices and condiments - Spectrophotometric determination of the extractable colour in paprika (ISO 7541:2020)
SN EN 12472-2021 Method for the simulation of accelerated wear and corrosion for the detection of nickel release from coated items
SN EN ISO 1463:2021 Metallic and oxide coatings - Measurement of coating thickness - Microscopical method (ISO 1463:2021)
SN EN ISO 1402:2021 Rubber and plastics hoses and hose assemblies - Hydrostatic testing (ISO 1402:2021)
SN EN ISO 1140:2021 Fibre ropes - Polyamide - 3-, 4-, 8- and 12-strand ropes (ISO 1140:2021)
SN EN ISO 6540:2021 Maize - Determination of moisture content (on milled grains and on whole grains) (ISO 6540:2021)
SN EN 143-2021 Respiratory protective devices - Particle filters - Requirements, testing, marking
SN EN ISO 21645:2021 Solid recovered fuels - Methods for sampling (ISO 21645:2021)
SN EN ISO 19628:2021 Fine ceramics (advanced ceramics, advanced technical ceramics) - Thermophysical properties of ceramic composites - Determination of specific heat capacity (ISO 19628:2017)
SN EN ISO 4120:2021 Sensory analysis - Methodology - Triangle test (ISO 4120:2021)
SN EN 4036-2021 Aerospace series - Rod end, adjustable, with self-aligning double row ball bearing and threaded shank, in corrosion resisting steel, reduced internal radial clearance - Dimensions and loads
SN EN ISO 14008:2021 Monetary valuation of environmental impacts and related environmental aspects (ISO 14008:2019)
SN EN 6025-2021 Aerospace series - Plates - Aluminium alloy 2024 - Close tolerances flatness - Thickness - 6 mm
SN EN 3572-2021 Aerospace series - PTFE flexible hose assembly with convoluted inner tube of a nominal pressure up to 6800 kPa and 8°30' fitting in titanium - Product standard
SN EN 17462-2021 Animal feeding stuffs: Methods of sampling and analysis - Determination of the radionuclides Iodine-131, Caesium-134 and Caesium-137 in feed
SN EN ISO 24266:2021 Footwear - Test methods for whole shoe - Flexing durability (ISO 24266:2020)
SN EN 17343-2021 Railway applications - General terms and definitions
SN EN ISO 10703:2021 Water quality - Gamma-ray emitting radionuclides - Test method using high resolution gamma-ray spectrometry (ISO 10703:2021)
SN EN 17226-2021 Beauty Salon Services - Requirements and recommendations for the provision of service
SN EN ISO 20888:2021 Dentistry - Vocabulary and designation system for forensic oro-dental data (ISO 20888:2020)
SN EN ISO 20323:2021 Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical properties of ceramic composites at ambient temperature in air atmospheric pressure - Determination of tensile properties of tubes (ISO 20323:2018)
SN EN ISO 13162:2021 Water quality - Carbon 14 - Test method using liquid scintillation counting (ISO 13162:2021)
SN EN 17476-2021 Specifications for dedicated liquefied petroleum gas appliances - LPG vapour pressure appliances incorporating a horizontal cartridge in the chassis
SN EN ISO 9235:2021 Aromatic natural raw materials - Vocabulary (ISO 9235:2021)
SN EN ISO 19223:2021 Lung ventilators and related equipment - Vocabulary and semantics (ISO 19223:2019)
SN EN ISO 22515:2021 Water quality - Iron-55 - Test method using liquid scintillation counting (ISO 22515:2021)
SN EN 17267-2021 Energy measurement and monitoring plan - Design and implementation - Principles for energy data collection
SN EN ISO 17511:2021 In vitro diagnostic medical devices - Requirements for establishing metrological traceability of values assigned to calibrators, trueness control materials and human samples (ISO 17511:2020)
SN EN ISO 22516:2021 Paints and varnishes - Practical determination of non-volatile and volatile matter content during application (ISO 22516:2019)
SN EN 12493-2021 LPG equipment and accessories - Welded steel pressure vessels for LPG road tankers - Design and manufacture
SN EN ISO 23411:2021 Small craft - Steering wheels (ISO 23411:2020)
SN EN ISO 16929:2021 Plastics - Determination of the degree of disintegration of plastic materials under defined composting conditions in a pilot-scale test (ISO 16929:2021)
SN EN ISO 3861:2021 Rubber hoses and hose assemblies for sand and grit blasting - Specification (ISO 3861:2021)
SN EN 15625-2021 Railway applications - Braking - Automatic variable load sensing devices
SN EN ISO 8469:2021 Small craft - Non-fire-resistant fuel hoses (ISO 8469:2021)
SN EN ISO 4823:2021 Dentistry - Elastomeric impression and bite registration materials (ISO 4823:2021)
SN EN ISO 22153:2021 Electric actuators for industrial valves - General requirements (ISO 22153:2020)
SN EN 14112-2021 Fat and oil derivatives - Fatty Acid Methyl Esters (FAME) - Determination of oxidation stability (accelerated oxidation test)
SN EN ISO 19902:2021 Petroleum and natural gas industries - Fixed steel offshore structures (ISO 19902:2020)
SN EN ISO 11063:2021 Soil quality - Direct extraction of soil DNA (ISO 11063:2020)
SN EN 13834-2021 Cookware - Ovenware for use in traditional domestic ovens
SN EN 13262-2021 Railway applications - Wheelsets and bogies - Wheels - Product requirements
SN EN ISO 9463:2021 Nuclear energy - Nuclear fuel technology - Determination of plutonium in nitric acid solutions by spectrophotometry (ISO 9463:2019)
SN EN ISO 14705:2021 Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for hardness of monolithic ceramics at room temperature (ISO 14705:2016)
SN EN ISO 18530:2021 Health Informatics - Automatic identification and data capture marking and labelling - Subject of care and individual provider identification (ISO 18530:2021)
SN EN ISO 23306:2021 Specification of liquefied natural gas as a fuel for marine applications (ISO 23306:2020)
SN EN 4864-2021 Aerospace series - Environmental testing - High dynamic abrasion, mar, scratch and punch test in cabin interior
SN EN ISO 19630:2021 Fine ceramics (advanced ceramics, advanced technical ceramics) - Methods of test for reinforcements - Determination of tensile properties of filaments at ambient temperature (ISO 19630:2017)
SN EN 17233-2021 Water quality - Guidance for assessing the efficiency and related metrics of fish passage solutions using telemetry
SN EN ISO 25065:2021 Systems and software engineering - Software product Quality Requirements and Evaluation (SQuaRE) - Common Industry Format (CIF) for Usability: User requirements specification (ISO 25065:2019)
SN EN ISO 14501:2021 Milk and milk powder - Determination of aflatoxin M1 content - Clean-up by immunoaffinity chromatography and determination by high-performance liquid chromatography (ISO 14501:2021)
SN EN 17429-2021 Conservation of cultural heritage - Procurement of conservation services and works
SN EN 17556-2021 Inland navigation vessels - Safety rota and safety plans for passenger vessels
SN EN ISO 473:2021 Lithopone pigments - General requirements and methods of testing (ISO 473:2019)
SN EN ISO 6321:2021 Animal and vegetable fats and oils - Determination of melting point in open capillary tubes - Slip point (ISO 6321:2021)
SN EN 17507-2021 Road vehicles - Portable Emission Measuring Systems (PEMS) - Performance assessment
SN EN ISO 22854:2021 Liquid petroleum products - Determination of hydrocarbon types and oxygenates in automotive-motor gasoline and in ethanol (E85) automotive fuel - Multidimensional gas chromatography method (ISO 22854:2021)
SN EN 12331-2021 Food processing machinery - Mincing machines - Safety and hygiene requirements
SN EN 17191-2021 Children's Furniture - Seating for children - Safety requirements and test methods
SN EN 16524-2021 Mechanical products - Methodology for reduction of environmental impacts in product design and development
SN EN 17446-2021 Fire extinguishing systems in commercial kitchens - System design, documentation, and test requirements
SN EN ISO 276:2021 Binders for paints and varnishes - Linseed stand oil - Requirements and methods of test (ISO 276:2019)
SN EN ISO 4518:2021 Metallic coatings - Measurement of coating thickness - Profilometric method (ISO 4518:2021)
SN EN 17203-2021 Foodstuffs - Determination of citrinin in food by HPLC-MS/MS
SN EN ISO 844:2021 Rigid cellular plastics - Determination of compression properties (ISO 844:2021)
SN EN ISO 13297:2021 Small craft - Electrical systems - Alternating and direct current installations (ISO 13297:2020)
SN EN ISO 13736:2021 Determination of flash point - Abel closed-cup method (ISO 13736:2021)
SN EN 437-2021 Test gases - Test pressures - Appliance categories
SN EN ISO 27587:2021 Leather - Chemical tests - Determination of free formaldehyde in process auxiliaries (ISO 27587:2021)
SN EN 13423-2021 Natural gas vehicles - Requirements for NGV workshops and the management of compressed natural gas (CNG) vehicles
SN EN ISO 20127:2021 Dentistry - Physical properties of powered toothbrushes (ISO 20127:2020)
SN EN ISO 17871:2021 Gas cylinders - Quick-release cylinder valves - Specification and type testing (ISO 17871:2020)
SN EN ISO 7376:2021 Anaesthetic and respiratory equipment - Laryngoscopes for tracheal intubation (ISO 7376:2020)
SN EN ISO 18086:2021 Corrosion of metals and alloys - Determination of AC corrosion - Protection criteria (ISO 18086:2019)
SN EN 14105-2021 Fat and oil derivatives - Fatty Acid Methyl Esters (FAME) - Determination of free and total glycerol and mono-, di-, triglyceride contents
SN EN 4689-2021 Aerospace series - Paints and varnishes - Two-components room temperature curing polyurethane finish - High flexibility and chemical agent resistance for military application
SN EN ISO 8666:2021 Small craft - Principal data (ISO 8666:2020)
SN EN ISO 21976:2021 Packaging - Tamper verification features for medicinal product packaging (ISO 21976:2018)
SN EN ISO 10477:2021 Dentistry - Polymer-based crown and veneering materials (ISO 10477:2020)
SN EN 15009-2021 Aerosol containers - Compartmented aerosol dispensers
SN EN 17127-2021 Outdoor hydrogen refuelling points dispensing gaseous hydrogen and incorporating filling protocols
SN EN 17387-2021 Chemical disinfectants and antiseptics - Quantitative test for the evaluation of bactericidal and yeasticidal and/or fungicidal activity of chemical disinfectants in the medical area on non-porous surfaces without mechanical action - Test method and requi
SN EN ISO 19734:2021 Eye and face protection - Guidance on selection, use and maintenance (ISO 19734:2021)
SN EN 841-2021 Bar coding - Symbology specifications - Format description
SN EN ISO 22970:2021 Paints and varnishes - Test method for evaluation of adhesion of elastic adhesives on coatings by peel test, peel strength test and tensile lap-shear strength test with additional stress by condensation test or cataplasm storage (ISO 22970:2019)
SN EN 17128-2021 Light motorized vehicles for the transportation of persons and goods and related facilities and not subject to type-approval for on-road use - Personal light electric vehicles (PLEV) - Requirements and test methods
SN EN ISO 18610:2021 Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical properties of ceramic composites at ambient temperature in air atmospheric pressure - Determination of elastic properties by ultrasonic technique (ISO 18610:2016)
SN EN 17104-2021 Thermoplastics rigid protective wallcovering panels for internal use in buildings - Performance characteristics
SN EN 16429-2021 Stationary source emissions - Reference method for the determination of the concentration of gaseous hydrogen chloride (HCl) in waste gases emitted by industrial installations into the atmosphere
SN EN ISO 21802:2021 Assistive products - Guidelines on cognitive accessibility - Daily time management (ISO 21802:2019)
SN EN ISO 56003:2021 Innovation management - Tools and methods for innovation partnership - Guidance (ISO 56003:2019)
SN EN ISO 14160:2021 Sterilization of health care products - Liquid chemical sterilizing agents for single-use medical devices utilizing animal tissues and their derivatives - Requirements for characterization, development, validation and routine control of a sterilization pr
SN EN ISO 22579:2021 Infant formula and adult nutritionals - Determination of fructans - High performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) after enzymatic treatment (ISO 22579:2020)
SN EN ISO 15995:2021 Gas cylinders - Specifications and testing of LPG cylinder valves - Manually operated (ISO 15995:2021)
SN EN 12353-2021 Chemical disinfectants and antiseptics - Preservation of test organisms used for the determination of bactericidal (including Legionella), mycobactericidal, sporicidal, fungicidal and virucidal (including bacteriophages) activity
SN EN 676-2021 Forced draught burners for gaseous fuels
SN EN 17278-2021 Natural gas vehicles - Vehicle fuelling appliances
SN EN ISO 14557:2021 Fire-fighting hoses - Rubber and plastics suction hoses and hose assemblies (ISO 14557:2021)
SN EN ISO 21187:2021 Milk - Quantitative determination of microbiological quality - Guidance for establishing and verifying a conversion relationship between results of an alternative method and anchor method results (ISO 21187:2021)
SN EN 482-2021 Workplace exposure - Procedures for the determination of the concentration of chemical agents - Basic performance requirements
SN EN 13749-2021 Railway applications - Wheelsets and bogies - Method of specifying the structural requirements of bogie frames
SN EN 14387-2021 Respiratory protective devices - Gas filter(s) and combined filter(s) - Requirements, testing, marking
SN EN ISO 22636:2021 Adhesives - Adhesives for floor coverings - Requirements for mechanical and electrical performance (ISO 22636:2020)
SN EN ISO 9093:2021 Small craft - Seacocks and through-hull fittings (ISO 9093:2020)
SN EN 15188-2021 Determination of the spontaneous ignition behaviour of dust accumulations
SN EN 14222-2021 Stainless steel steam boilers
SN EN 12569-2021 Industrial valves - Valves for chemical and petrochemical process industry - Requirements and tests
SN EN ISO 5079:2021 Textile fibres - Determination of breaking force and elongation at break of individual fibres (ISO 5079:2020)

Standards Norway

SN/TS 9406:2021 Fish and fish products - Fresh Skrei (Spawning cod) - Product requirements
SN-CWA 17664:2021 Lower-limb wearable devices - Performance test method for walking on uneven terrain
SN-CWA 17675:2021 Mapping of the mandatory and voluntary carbon management framework in the EU
SN-NSPEK 3031:2021 Energy performance of buildings - Calculation of energy needs and energy supply

Others: sn2021