Vehicle Exhaust Emissions & LEV

Engine-Matched Extraction Sizing Excel Calculator

A Practical Tool for Designing and Assessing Vehicle Exhaust LEV Systems

Vehicle exhaust emissions are a significant occupational health hazard in garages, workshops, depots, MOT stations, and testing facilities. Petrol, diesel, LPG, and other internal combustion engines emit a complex mixture of toxic gases and hazardous particulates, many of which are invisible yet capable of causing serious short- and long-term health effects.

Effective vehicle exhaust extraction (LEV) is therefore a critical engineering control — but only when it is correctly sized, correctly applied, and properly understood.

This Excel calculator was developed to support real-world LEV design and assessment decisions, helping practitioners match extraction capacity to engine size and operating conditions, rather than relying on guesswork or over-simplified assumptions.

A Practical Sizing Tool Based on Recognised Guidance

The calculator is based on principles and reference values drawn from:

• EGEA Guidelines (European Garage Equipment Association)

• HSE HSG187 – Control of diesel engine exhaust emissions

• HSG258 – Local Exhaust Ventilation

• Established LEV engineering practice

It provides a structured way to estimate required exhaust extraction volumes based on:

• Engine size (litres / capacity)

• Engine speed (rpm)

• Vehicle type (cars, vans, trucks)

• Typical operating scenarios (idling, testing, higher rpm)

The aim is to help ensure systems are neither under-extracting nor excessively over-powered.

Why Correct Sizing Matters

Most guidance focuses on avoiding under-extraction — but over-extraction carries risks too.

This tool is designed to support balanced design, recognising that extraction systems must remove what is needed — no less, but also no more than necessary.

Risks of Under-Extraction

• Exhaust gases and particulates escape into the workspace

• Increased exposure to CO, NOx, diesel particulate matter (DEEEs)

• Failure to adequately control exposure under COSHH

• Odour, irritation, soot deposition

Risks of Over-Extraction

• Altered exhaust back pressure, affecting engine behaviour

• Poor performance of catalytic converters or particulate filters

• Excessive cooling of exhaust systems (cold start issues, condensation)

• Mechanical strain on exhaust components and hoses

• Increased energy use, noise, and operating costs

This calculator helps practitioners understand and avoid both extremes.

Designed for LEV Practitioners — Not Black-Box Outputs

The calculator supports professional judgement rather than replacing it.

It helps users:

• Estimate appropriate extraction airflow (m³/h)

• Compare system capacity with engine demand

• Sense-check installed LEV systems

• Support defensible design and Reg 9 assessment decisions

It is particularly useful when reviewing:

• Fixed tailpipe extraction systems

• Hose and clip-on scavenger systems

• Multi-branch extraction systems

• Workshop bays where multiple vehicles may connect simultaneously

Supporting COSHH & LEV Assessment Work

The calculator complements broader LEV duties by supporting:

• COSHH risk assessments

• LEV system design and specification

• Commissioning checks

• COSHH Regulation 9 Thorough Examination and Test (TExT)

• Investigation of complaints, visible emissions, or odour issues

It aligns with the principle that exhaust emissions must be captured at source, rather than relying on general ventilation or open doors.

Important Professional Notes & Limitations

This tool is provided as a reference and calculation aid only.

• Every effort has been made to minimise errors

• No guarantee is given that the spreadsheet is error-free

• No liability is accepted for its use

• Users must understand the assumptions behind the calculations

• Results must be sense-checked and verified

The calculator does not replace:

• A site-specific risk assessment

• Proper LEV design

• Commissioning and performance testing

• Professional competence

Why This Tool Matters

Incorrectly sized vehicle exhaust LEV systems can lead to:

• Ongoing exposure to carcinogenic diesel exhaust emissions

• Poor confidence in LEV performance

• Conflicting test results year-on-year

• Enforcement, compliance, or audit challenges

This calculator supports clear thinking, transparent justification, and defensible decisions — whether you are designing, inspecting, or testing exhaust extraction systems.

Who This Calculator Is For

This Excel tool is intended for:

• LEV engineers and COSHH Reg 9 testers

• Occupational hygienists

• Garage and workshop designers

• Health & safety professionals

• Duty holders responsible for vehicle exhaust control

It is particularly relevant for those working in garages, depots, MOT stations, fleet workshops, and testing facilities.

Product Details

• Product: Vehicle Exhaust Emissions & LEV – Excel Calculator and notes

• Format: Microsoft Excel spreadsheet and PDF notes

• Focus: Engine-matched exhaust extraction sizing

• Based On: EGEA guidance, HSE HSG187, HSG258

• Use Case: LEV design, assessment, and TExT support

• Author: Louise Davies Wood

• Release: September 2025