Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

Ventilation Systems

Design of systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.

Sponsored Links

Air - Density and Specific Volume vs. Altitude

Density and specific volume of air varies with elevation above sea level.

Air Change Rate

Calculate air change rates - equations in imperial and SI units.

Air Change Rates in typical Rooms and Buildings

Fresh air (make up air) rquirements - or recommended air change rates (ACH) for typical rooms and buildings like auditoriums, kitchens, churches and more.

Air Curtains or Air Screens

Calculate air curtains or air screens in open doorways used to keep acceptable indoor comfort in buildings.

Air Duct Calculator

Online calculator to compute friction loss in air ducts.

Air Duct Components - Minor Dynamic Loss Coefficients

Minor loss (pressure or head loss) coefficients for air duct components.

Air Duct Velocities

Typical air duct velocities in applications like ventilation systems or compressed air systems.

Air Ducts - Friction Loss Diagram

A major friction loss diagram for air ducts - Imperial units ranging 10 - 100 000 cfm.

Air Ducts - Friction Loss Diagram

A major friction loss diagram for air ducts - in imperial units ranging 10 000 - 400 000 cfm.

Air Ducts - Friction Loss Diagram

A major friction loss diagram for air ducts - SI units.

Air Ducts - Major Friction Head Loss, Online Calculator

Head loss or major loss in air ducts - equations and online calculator for rectangular and circular ducts - Imperial and SI units.

Air Ducts - Major Friction Loss vs. Temperature and Pressure

The influence of temperature and air pressure on major friction loss.

Air Ducts - Minor Loss Coefficient Diagrams

Minor loss coefficient diagrams for air ductwork, bends, expansions, inlets and outletsĀ  - SI units.

Air Ducts - Sizing

Required duct area vs. air flow.

Air Ducts - Velocity Diagram

Air flow volume, duct size, velocity and dynamic pressure.

Air Filters - Arrestance and Efficiency

Air filters efficiency and arrestance.

Air Heating Systems

Air heating buildings - heat supply vs. air flow and temperature.

Air Intakes and Outlets

Ventilation systems - air intakes and outlets - rules of thumbs.

ASHRAE - American Society of Heating, Refrigerating and Air-Conditioning Engineers

ASHRAE Standards.

Belt driven Fans - Fan vs. Motor Speed

Fan vs. motor speed in belt driven fans.

Belt Transmissions - Speed and Length of Belts

Calculate length and speed of belt and belt gearing.

Carbon Dioxide Concentration in Rooms Occupied with People

Carbon dioxide concentration in a room may indicate air quality and ventilation system efficiency.

Carbon Monoxide and Health Effects

Exposure to Carbon Monoxide - CO and health effects.

Circular Ducts - Dimensions

Standard size of circular ventilation air ducts.

Classification of Ventilation Systems

Ventilation systems can be classified by functions, distribution strategies or by ventilation principles.

Clean Rooms - Federal Standard 209

Clean rooms virtually free of contaminants like dust or bacteria.

Clean Rooms - ISO Standard 14644

Clean room class limits according ISO Standard 14644-1.

Colebrook Equation

Friction loss coefficients in pipes, tubes and ducts.

Comfort Environments - Selecting Ventilation System

A quick selection guide of ventilation system in comfort environments.

Design of Ventilation Systems

Design procedure for ventilation systems - air flow rates, heat and cooling loads, air shifts according occupants, air supply principles.

Duct Sizing - the Equal Friction Method

The equal friction method for sizing air ducts is easy and straightforward to use.

Duct Systems - Pressure Classifications

Duct systems are commonly divided into three pressure classifications.

Duct Velocity

Calculate velocities in circular and rectangular ducts - imperial and SI-units - online calculator.

Ducts - Cross-Sectional Area vs. Diameter

Circular ducts sross-sectional areas.

Ducts - Sheet Metal Gauges

Thickness of sheet metal used in ductwork.

Ducts Sizing - the Velocity Reduction Method

The velocity reduction method can be used when sizing air ducts.

Ductwork - Seal Classes

Ductwork air leakage classes.

Ductwork - Supports

Recommended distance between ductwork support hangers.

Energy Equation - Pressure Loss vs. Head Loss

Calculate pressure loss - or head loss - in ducts, pipes or tubes.

Equivalent Diameter - Rectangular vs. Circular HVAC Ducts

Rectangular equivalent diameter for air flows between 100 - 50000 cfm.

Evacuation of Air - minimum Capture Velocities to avoid Pollution products transferred to the Room

Capture velocities to avoid pollution products from galvanic baths, spray painting boxes and more contaminating the surrounding room and environment.

Exhaust Hoods

Sizing of exhaust hoods - air volume flow and capture velocities - online exhaust hood calculator.

Exhaust Outlets - Capturing Air Velocities

Capturing air velocity in front of an exhaust outlet - online exhaust outlet velocity calculator.

Fan Affinity Laws

The affinity laws can be used to calculate resulting volume capacity, head or power consumption when speed or wheel diameters are changed.

Fan AMCA Classification

Fan classification established by AMCA.

Fan Capacity Diagrams

Pressure, head, air flow volume and fan capacity diagrams.

Fan Inlets - Air Density vs. Suction Pressure

High suction pressure at a fan inlet decreases the density of air - and should be corrected for proper selection of the fan.

Fan Motors - Starting Torques

The motor must be capable of accelerating the fan wheel to it's operating speed.

Fans - Calculate Air and Brake Horsepower

AHP - Air Horse Power and BHP - Brake Horse Power.

Fans - Capacity Control

How to modulate fans and their capacities.

Fans - Efficiency and Power Consumption

Power consumption and typical efficiencies of fans

Fans - Troubleshooting

Guide to troubleshooting fan problems.

Fans - Volume Flow, Pressure Head and Power Consumption vs. Air Temperature and Density

The temperature and density of the air influences on the volume flow, pressure head and power consumption in a fan.

Fluid Flow - Equivalent Diameter

Convert rectangular and oval duct geometry to a equivalent circular diameter - online calculator with imperial and SI-units.

Fluid Flow - Hydraulic Diameter

Calculate hydraulic diameter for pipes and ducts.

Free Area Ventilation

Ventilation required for attic areas.

Garage Ventilation

Exhaust ventilation from garages and workshops.

Gas Vent Termination - Clearance vs. Roof Slope

Clearance tolerance for gas vent terminations vs. roof slope.

Heat Recovery

Ventilation and heat-recovery calculations, sensible and latent heat - online calculators - imperial units.

Heat Recovery Efficiency

Classification of heat recovery efficiencies - temperature efficiency, moisture efficiency and enthalpy efficiency - online heat exchanger efficiency calculator.

Heaters and Coolers in Ventilation Systems

Basic equations for heat transfer - selecting criteria for heaters and coolers in ventilations systems.


Sprayed coils, spinning discs and steam humidifiers.

HVAC Dampers - Pressure Loss

Pressure head loss in HVAC dampers.

HVAC Diagram - Online Drawing Tool

Draw HVAC diagrams online with this Google Drive drawing tool.

HVAC Ducts - Air Velocities

Recommended air velocities in HVAC ducts.

Indoor Design Temperatures

Recommended indoor temperatures in summer or winter.

Industrial Environments - Selecting Ventilation System

A quick selection guide for ventilation systems/principles in industrial environments.

Industrial Product and Production Processes - Climate Conditions

Recommended indoor temperature and humidity for common industrial products and production processes.

Mechanical Energy Equation vs. Bernoulli Equation

The Mechanical Energy Equation compared to the Extended Bernoulli Equation.

Natural Draft - Air Flow Volume and Velocity

Air flow - volume and velocity - due to stack or flue effect caused by indoor hot and outdoor cold temperature difference.

Odor from Persons - Required Ventilation

Required air ventilation to handle odor and smell from persons.

Odor Intensity from Persons

Odor intensity from persons vs. room volume and ventilation.

Outdoor Makeup Air

Acceptable indoor air quality and required make up air.

Outdoor Supply Air Rates

Recommended supply air rates of outdoor air - with or without smoking - in rooms like banks, assembly halls, hotels and many more.

Pollution Concentration in Rooms

Concentration of a pollution in a limited space as a room depends on the amount of polluted material spread in the room, supply of fresh air, outlets positions and construction, principles used for supply and outlet from the space.

Pumps vs. Compressors, Blowers and Fans

The difference between pumps, compressors, blowers and fans.

Rectangular Air Ducts - Velocity Diagram

Velocity diagram for rectangular air ducts - metric units.

Rectangular Ducts - Dimensions

Commonly used metric dimensions for rectangular air ducts in ventilation systems.

Rectangular Ducts - Hydraulic Diameter

Calculate hydraulic diameter for rectangular ducts - metric units.

Relative Humidity in Production and Process Environments

Recommended relative humidity in production and process environments - like libraries, breweries, storages and more.

Required Air Flow to Remove Moisture

Air flow required to remove vapor production from a room.

Required Building Space per Person

Room area per person - may be used to calculate typical indoor climate loads.

Roughness & Surface Coefficients

Surface coefficients that can be used to calculate friction and major pressure loss for fluid flow with surfaces like concrete, galvanized steel, corroded steel and more.

Scrubber Basics

In a wet scrubber process air is drawn through a mist of water made by spray nozzles, then through separators where water droplets with dust and particles are removed.

Sizing Circular Ducts

A rough guide to maximum air volume capacity of circular ducts in comfort, industrial and high speed ventilation systems.

Spiral Duct Elbows - Weights

Ductwork - weight of galvanized round spiral elbows.

Spiral Ducts - Dimensions

Standard dimensions of spiral ducts - Imperial units.

Stack or Flue Effect

The stack or flue effect occurs when the outdoor temperature is lower than indoor temperature.

STP - Standard Temperature and Pressure and NTP - Normal Temperature and Pressure

The definition of STP - Standard Temperature and Pressure and NTP - Normal Temperature and Pressure.

Types of Fans

Axial and propeller fans, centrifugal (radial) fans, mixed flow fans and cross flow fans.

Types of Fans - Capacity Ranges

Centrifugal, axial and propeller fans and their capacity ranges.

U-Tube Differential Pressure Manometers

Inclined and vertical u-tube manometers used to measure differential pressure in flow meters like pitot tubes, orifices and nozzles.

Velocity Classification of Ventilation Ducts

Recommended air velocities in ventilation ducts

Ventilation and Air Conditioning Equipment - Area Required

Required size of ventilation and air conditioning rooms according DIN 1946.

Ventilation Components - Minor Pressure Loss

Pressure loss in ventilation system components like dampers, filters, heaters, coolers and more.

Ventilation Dampers - Classification

Dampers in ventilation systems may be classified through function, construction or leakage class.

Ventilation Ducts - Minor Loss Resistance

Minor pressure or head loss in ventilation ducts vs. air velocity - minor loss coefficient diagram.

Ventilation Efficiency

The efficiency of a ventilation system may be related to temperature and/or pollution concentrations.

Ventilation Filters

Classification of air filters used in ventilation systems.

Ventilation Principles

Some commonly used ventilation principles - short cut, mixed air, displacement and piston principle.

Ventilation Systems - Return Intakes

Size and capacities of air return intakes.

Sponsored Links

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.