UNI EN 257 : 2010

Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Classification
5 Units of measurement and test conditions
6 Construction requirements
7 Performance
8 EMC/Electrical requirements
9 Marking, installation and operating instructions
Annex A (informative) - Gas connections in common use in
  the various countries
Annex B (informative) - Leak-tightness test - volumetric
  method
Annex C (informative) - Leak-tightness test - pressure loss
  method
Annex D (normative) - Conversion of pressure loss into leakage
  rate
Annex E (normative) - Electrical/electronic component fault
  modes
Annex F (normative) - Additional requirements for safety
  accessories and pressure accessories as defined in EU
  Directive 97/23/EC
Annex G (normative) - Materials for pressurized parts
Annex H (informative) - Additional materials for pressurized
  parts
Annex I (normative) - Requirements for controls used in DC
  supplied gas burners and gas burning appliances
Annex ZA (informative) - Relationship between this European
  Standard and the Essential Requirements of EU Directive
  2009/142/EC relating to appliances burning gaseous fuels
Bibliography

Describes the safety, construction and performance requirements for mechanical thermostats intended for use with gas appliances and similar use, hereafter referred to as 'thermostats'.