LEV107 - Basic LEV maths (v1.4)

Mathematics sits at the heart of every effective Local Exhaust Ventilation (LEV) system — yet it’s one of the areas that causes the most uncertainty in the field.

From duct sizing and airflow calculations to understanding velocity, pressure, and density, LEV maths quietly determines whether a system controls exposure or merely looks like it should. And when the maths is misunderstood — or skipped altogether — the consequences show up quickly: poor capture, unstable systems, failed examinations, and unnecessary risk to health.

LEV107: Basic LEV Maths was written to change that.

This guide strips LEV mathematics back to its engineering fundamentals, explaining not just what to calculate, but why those calculations matter and where they apply during design, testing, and COSHH Regulation 9 Thorough Examination and Test (TExT).

A Practical Engineering Guide — Not a Maths Textbook

LEV107 is not academic maths and it’s not theory for theory’s sake.

It’s a field-focused, metric-based engineering guide, written specifically for LEV practitioners who need to apply calculations confidently during real-world work.

Inside, you’ll find clear explanations and worked examples covering:

• Mathematical terms used in LEV — explained without jargon

• Working correctly in metres (and why it matters)

• Circles, areas, and duct geometry

• Calculating duct diameter from area

• The Velocity–Volume–Area relationship

• Static, velocity, and total pressure relationships

• Velocity pressure and air velocity

• Standard and non-standard air density conditions

• Practical correction factors

• Common conversion factors used in LEV testing

Each section builds logically, helping you understand how individual calculations link together to form a complete picture of system performance.

Why LEV Maths Matters

LEV systems don’t fail randomly — they fail because the numbers don’t add up.

Common issues seen during TExT often trace back to basic mathematical misunderstandings:

• Duct velocities that look acceptable but are calculated incorrectly

• Flowrates that don’t align with hood design intent

• Pressure readings that are misinterpreted or compared incorrectly

• Hot air systems assessed using standard air assumptions

• Fan performance judged without understanding total pressure

LEV107 helps practitioners recognise these issues early, giving you the confidence to question results, validate performance, and justify your conclusions clearly and defensibly.

Who This Guide Is For

LEV107 is ideal for:

• LEV engineers and testers

• Occupational hygienists

• Designers and installers

• Trainee LEV practitioners

• Anyone involved in COSHH compliance and exposure control

Whether you’re new to LEV or looking to strengthen your technical foundation, this guide provides the maths you actually use — explained in a way that finally makes sense.

Product Details

• Title: LEV107: Basic LEV Maths

• Edition: Third Edition

• Format: Digital guide (PDF)

• Focus: Metric-based LEV mathematics

• ISBN: 978-1-9192558-0-4

• Author: Louise Davies Wood

• Published: 2025