Useful Excel Calculator - Foundry canopy hood design (Rectangular and Circular hoods)

Designing canopy hoods for hot processes is a routine part of LEV work in foundries and heavy industry — yet it’s also an area where small assumptions or rushed calculations can lead to significant under-performance.

Estimating buoyant plume flow.
Allowing for plume spread with hood height.
Translating ACGIH equations into practical hood sizes and airflow rates.
Sense-checking results under design or site pressure.

The Canopy Hood Sizing Excel Calculator for Hot Processes was created as a practical support tool for LEV practitioners who want a structured, transparent way to size canopy hoods while retaining full ownership of the engineering judgement behind the design.

This is not a black-box calculator. It is a clear, formula-based worksheet that mirrors the ACGIH Industrial Ventilation Manual methodology used in everyday LEV design work.

A Simple, Structured Canopy Hood Calculation Tool

The calculator is laid out to follow the logical steps used when sizing canopy (receiving) hoods over hot processes, including furnaces, molten metal operations, and high-temperature equipment.

Core Calculations Covered

The spreadsheet guides the user through the key parameters influencing canopy hood performance:

Hypothetical source dimensions
Based on source size and hood elevation, reflecting plume expansion.

Temperature difference (ΔT)
Capturing the effect of buoyancy driven by hot processes relative to ambient air.

Source-induced airflow
Estimating plume flow generated by thermal updraft.

Total required hood airflow (Q)
Calculating the volumetric flowrate required at the hood face, including allowance for entrainment and practical capture.

Minimum hood dimensions
Ensuring the canopy hood is sized to intercept the full plume at hood level.

Both rectangular and cylindrical sources can be assessed using the same framework.

Based on ACGIH Industrial Ventilation Guidance

The calculations are aligned with the methodology set out in the ACGIH Industrial Ventilation: A Manual of Recommended Practice for Design, widely regarded as the benchmark reference for LEV design.

This calculator converts the published equations into a usable, repeatable format — reducing manual manipulation while maintaining full transparency.

Designed for Reliability — Not Accidental Changes

To support consistent and defensible calculations:

• All formula cells are locked

• Input cells are clearly identified

• The worksheet structure is fixed

This prevents accidental overwriting and ensures the calculator behaves the same way every time it is used.

Important Professional Note

This calculator is provided as a design aid only.

While care has been taken to implement the formulas correctly, no guarantee can be given that the spreadsheet is free from errors. Users are expected to:

• Understand the underlying ACGIH methodology

• Sense-check all outputs

• Verify results manually where appropriate

• Apply professional judgement at all times

No responsibility is accepted for decisions made solely on the basis of the calculator output. Feedback on any identified errors is welcomed.

Why This Tool Matters

In hot process LEV design, small errors can lead to:

• Undersized canopy hoods

• Inadequate capture of buoyant fumes

• Excessive heat and contaminant escape into the workspace

• Over- or under-specified exhaust systems

• Difficult-to-defend design assumptions

This calculator helps reduce avoidable mistakes, improve consistency, and support clearer design thinking — while keeping responsibility firmly with the practitioner.

Who This Calculator Is For

This Excel calculator is suitable for:

• LEV engineers and designers

• Industrial ventilation consultants

• Occupational hygienists

• Foundry and heavy-industry safety professionals

• Trainee LEV practitioners learning canopy hood design

It is particularly useful when working with hot, buoyancy-driven processes where receiving hoods are the appropriate control strategy.

Product Details

Product: Canopy Hood Sizing Excel Calculator for Hot Processes
Format: Microsoft Excel spreadsheet (.xlsx)
Calculation Method: ACGIH Industrial Ventilation (canopy hoods over hot processes)
Formulas: Locked to prevent accidental editing
Use Case: LEV design, design verification, training, and airflow justification
Author: Louise Davies Wood