⭐ Upgrade to Pro - £19
Unlock all lessons and mock exams to pass Level 2 + Level 3 theory exams.
Upgrade nowVentilation Categories & Calculations
Read through the material below, then test your understanding.
Module Lessons
Domestic Fuel Systems, Combustion & Flues
Fuel Properties: Gas, LPG & Solid Fuel
Fuel Properties: Oil & Low-Carbon Alternatives
Storing Oil, Coal & LPG
Storing Biomass & General Fuel Storage
Fuel Delivery & Distribution
Complete & Incomplete Combustion
Carbon Monoxide Poisoning
Combustion & Ventilation Air Requirements
Ventilation Categories & Calculations
Ventilation for Open-Flued & Room-Sealed Appliances
Flueless Appliance Ventilation Calculations
Types of Chimney & Flue Systems
Open Flues & Flexible Liners
Flue Terminals & Builder's Openings
Terminal Guards, Flue Blocks & Ridge Terminals
Room-Sealed (Balanced) Flues
Effective Height & Flue Routing
Flue Temperature, Condensation & Termination
Class 1 & Class 2 Flue Construction
Rigid & Flexible Metallic Flue Systems
Flue Testing Procedures
Flue Gas Analysis
Lesson Overview
This guide covers the core ventilation categories, calculation methods, and conversion rules for domestic gas appliances under BS 5440-2.
Learning Objectives
Calculate free air requirements using gross and net heat inputs for various appliance configurations.
Apply adventitious ventilation deductions and identify when deductions are prohibited.
Determine correct free area sizing for compartments, vents in series, and multi-appliance installations.
Unlock the full lesson & knowledge check
Get lifetime access to every Level 2 & 3 lesson, 3500+ total questions, and timed City & Guilds mock exams.
Get Pro Access (£19)Already have Pro? Sign in
Interactive City & Guilds Level 2 and Level 3 plumbing lessons, flashcards and mock exams, built for UK students and professionals.
© 2026 PlumbingIQ. All rights reserved.