BSRIA Guide 49/2024 – Commissioning Air Systems
Updated Guidance – How to Functionally Test and Regulate Ventilation Systems
LEVCentral Expert Commentary
BSRIA BG 49 has long been regarded as one of the industry’s principal references for the commissioning of air distribution systems. The 2024 edition supersedes BG 49/2015 and reflects significant developments in commissioning practice, instrumentation, ventilation technologies and industry guidance.
Whilst primarily focused on building ventilation systems, many of the principles contained within BG 49 are directly relevant to LEV commissioning and performance verification. The guide reinforces the importance of moving beyond simple airflow measurements and adopting a structured approach to functional testing, regulation, documentation and performance verification.
Particularly valuable are the sections covering design for commissionability, airflow measurement techniques, test instrumentation, functional testing procedures and commissioning documentation. These topics align closely with the growing industry focus on demonstrable performance, commissioning evidence and assurance.
The publication also reflects the increasing complexity of modern ventilation systems, incorporating updated guidance on VAV and CAV systems, differential pressure systems, active chilled beams, hybrid ventilation and other specialist applications. For commissioning engineers, designers and duty holders, BG 49/2024 provides a comprehensive framework for demonstrating that installed systems perform as intended and that commissioning outcomes can be properly evidenced.
As the ventilation sector places increasing emphasis on performance verification and operational assurance, BG 49/2024 remains an essential reference document for anyone involved in commissioning air systems.
It also contains one of the best explanations of how to accurately balance LEV ducted systems using the “Proportional Balancing Method”
Source Document
Purchase the BSRIA Guide here:
Source: BSRIA
Document Type: Technical Guidance
Status: June 2024
Last reviewed by LEVCentral: June 2026
Key Learning Points
- BG 49/2024 supersedes BG 49/2015.
- Provides practical methodologies for commissioning LEV systems.
- Covers airflow measurement techniques and test instrumentation.
- Includes guidance on design for commissionability and installation requirements.
- Addresses modern ventilation technologies including VAV and CAV systems.
- Provides example commissioning methodologies and documentation templates.
- Supports compliance with the principles contained within CIBSE Commissioning Code A.
Further Resources
- CIBSE Commissioning Code A – Air Distribution Systems
- BSRIA BG 88/2025 – Commissioning Responsibilities Framework
- HSG258 – Controlling Airborne Contaminants at Work
- Defensible LEV Commissioning
Recommended Learning
- P600 Methods for Testing Performance of LEV
- P601 LEV Thorough Examination & Testing
- P602 LEV Basic Design Principles
- P604 Commissioning & Performance Evaluation of LEV
Thought Leadership
Modern commissioning is increasingly moving from a process of measurement towards a process of assurance. BG 49/2024 reflects this evolution by emphasising not only how systems should be tested and regulated, but how commissioning evidence should demonstrate that performance objectives have been achieved.
For organisations seeking defensible evidence of ventilation performance, commissioning is no longer simply a technical exercise—it is an essential part of the evidential chain supporting operational assurance.
