Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) – Approved Code of Practice and Guidance (L138)
L138 is the Health and Safety Executive’s Approved Code of Practice (ACOP) and guidance supporting the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).
The publication provides practical guidance on identifying, assessing and controlling the risks of fire, explosion and similar dangerous events arising from the use, storage or handling of flammable gases, vapours, mists, liquids and combustible dusts in the workplace. It is the principal guidance document used by employers, designers, engineers and safety professionals when implementing DSEAR requirements.
The guidance covers:
- DSEAR risk assessment requirements
- Hazardous area classification
- Control and mitigation measures
- Ventilation strategies
- Ignition source control
- Explosion protection measures
- Equipment selection for hazardous areas
- Safe systems of work and permit-to-work procedures
- Emergency planning and training requirements
This resource is relevant to:
- LEV Designers
- Commissioning Engineers
- Occupational Hygienists
- DSEAR Assessors
- Process Engineers
- Health & Safety Professionals
- Duty Holders
- Facilities Managers
Source Document
View the HSE guidance here:
Source: Health and Safety Executive (HSE)
Document Type: Guidance
Status: Current
Last reviewed by LEVCentral: June 2026
LEVCentral Expert Commentary
While often viewed as a specialist fire and explosion document, L138 has significant implications for the design, installation, commissioning and operation of LEV systems.
Many LEV systems are installed specifically to control flammable vapours, combustible dusts or explosive atmospheres. Designers and commissioning engineers should therefore understand how DSEAR requirements influence ventilation design, hazardous area classification, equipment selection and ongoing system maintenance.
Particular attention should be given to the sections covering:
- Hazardous area classification
- Ventilation and containment strategies
- Ignition source control
- Selection of ATEX equipment
- Combustible dust hazards
- Verification and inspection requirements
In practice, many LEV systems form part of a wider DSEAR control strategy. Consequently, LEV professionals should understand not only airflow performance requirements but also the fire and explosion risks associated with the substances being controlled.
Early collaboration between DSEAR assessors, process engineers, designers and commissioning specialists is often essential to ensure a defensible and compliant control solution.
Further Resources
- Area Classification for Explosive Atmospheres (HSE)
- HSE Dangerous Substances and Explosive Atmospheres Regulations (DSEAR)
- ATEX Equipment Guidance
- Centrifugal Fan – IACS Non-Sparking Standard
- Hazardous Area Classification for Dusts
- Explosion Protection in LEV Systems
Recommended Learning
- OXY103 DSEAR Awareness Training
- P602 LEV Design Principles
- P600 Methods for Testing Effectiveness of LEV
- ATEX Fundamentals
Thought Leadership
- Defensible LEV Commissioning
- LEV Governance and Duty Holder Assurance
- Commissioning vs TExT – Understanding the Difference
