Standard

Family name, INITIAL(S) (of standard author if applicable)/Organisation. Year. Standard number. Title of standard. Place of publication: Publisher.

The British Standards Institution is located in London and the International Standards Office in Geneva. For standards produced by other organisations, you should look for the location of their main office or headquarters and use this as the place of publication. 

Example:

British Standards Institution. 1990. BS5605:1990. Recommendations for citing and referencing published material. London: BSI.

International Standards Office. 2015. ISO9001:2015. Quality Management Systems. Geneva:ISO