CALCULATORS / PUMPS, FANS AND VENTILATION

Ventilation airflow calculator

Well-defined room volume and volumetric ventilation rate.

pumps-air-changes.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	volumem^3	changesh^-1
	50	4
	50	3.2

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

ventilation target example4.00 h^-1✓ passes

BASELINE INPUTS

flow200 m^3/hlength5 mwidth4 mheight2.5 m

CALCULATED

volume50 m^3

changes4 h^-1

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Ventilation airflow
# Scope: Well-defined room volume and volumetric ventilation rate.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

flow = 200 m^3/h
length = 5 m
width = 4 m
height = 2.5 m

volume := length*width*height [m^3]
changes := flow/volume [h^-1]

check ventilation target example: changes >= 3 h^-1

scenario alternative: flow = 160 m^3/h

Calculated from your source · not saved

Baseline · Baseline

ventilation target example4.00 h^-1 ✓ passes

alternative · alternative

ventilation target example3.20 h^-1 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

volume: volume = length*width*height [m^3]
changes: changes = flow/volume [h^-1]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

flow: 200 m^3/h
length: 5 m
width: 4 m
height: 2.5 m

Calculated

volume: 50 m^3
changes: 4 h^-1

Assumptions and limits

Well-defined room volume and volumetric ventilation rate.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Ventilation airflow. Inputs: room volume; target air changes per hour. Outputs: required volumetric airflow. Model scope: Measured or manufacturer curves and declared fluid conditions. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: room volume, target air changes per hour
Outputs: required volumetric airflow
Modes: calculate, compare, sweep
Drawing: System and equipment curves

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS