UNE updates Legionella standard for building systems based on experience gained in recent years

The Spanish Association for Standardisation (UNE) has published the new version of Standard UNE 100030:2026, Prevention and Control of Legionella Proliferation and Spread in Installations, replacing the 2023 edition and consolidating the most extensive technical developments to date in the prevention and control of Legionnaires' disease in Spain. The document was developed within UNE's Technical Committee on Air Conditioning (CTN-UNE 100), whose secretariat is managed by the Association of Air Conditioning Equipment Manufacturers (AFEC). More specifically, it was prepared by Working Group 12 of UNE Technical Standardisation Committee CTN 100, comprising a broad multidisciplinary team of engineers, biologists, pharmacists, chemists, veterinarians, doctors, technicians and industry specialists.

This new version was promoted and coordinated by AQUA España, the professional association of companies operating in the water and Legionella sector. Representatives of the main professional associations involved in the industry—FEDECAI, ANECPLA, CONAIF, AEFYT and ATECYR—also actively participated in the revision process, alongside experts from private-sector companies.

The main reason for updating the standard was the need to incorporate the experience accumulated since the entry into force of Royal Decree 487/2022 and its subsequent amendment by Royal Decree 614/2023. The aim is to provide consistent technical criteria that elaborate on aspects addressed only in general terms by the legislation, particularly those relating to the Legionella Health Plan (PSL) and risk assessment.

The new edition also incorporates practical experience gained in recent years, recommendations from the World Health Organization (WHO), contributions from the Ministry of Health and Spain's autonomous communities, and technological and engineering advances applicable to installations where there is a risk of Legionella proliferation.

Risk assessment

Among the main changes is a comprehensive update of Annex J, dedicated to risk assessment. It introduces a more precise methodology based on the different stages of an installation, including the creation of a Stage Risk Index (IRE) and an Overall Risk Index (IRG). The spreadsheet accompanying the standard has also been thoroughly revised to facilitate the practical implementation of Legionella Health Plans (PSLs).

Annex K has also been expanded and improved. It systematically sets out the content of the PSL, incorporating experience gained during the first years of implementing the new legislative framework, as well as recommendations and guidance provided by health authorities.

Another important addition to the 2026 edition is the new Annex M, entitled Technical Solutions for the Design of Centralised Domestic Hot Water (DHW) Systems. This new annex brings together hydraulic and thermal engineering criteria aimed at minimising the risk of Legionella proliferation from the initial design stage. It includes recommendations on storage tanks, thermal stratification, water renewal, recirculation, system balancing, renewable energy integration and practical design diagrams.

The final draft was approved by the plenary session of CTN-UNE 100, comprising more than 50 representatives from laboratories, associations, companies and public bodies. The process also benefited from significant institutional collaboration, with contributions coordinated by the Ministry of Health's Subdirectorate-General for Environmental Health, incorporating observations and improvements proposed by the health authorities of Spain's autonomous communities. In addition, the industrial safety departments of the Government of Catalonia and the Basque Government played a key role in promoting the development of the new Annex M on technical solutions for centralised domestic hot water systems.