Introduction to industrial ventilation (2023)

Ventilation is the mechanical system in a building that brings in “fresh” outdoor air and removes the “contaminated” indoor air.

In a workplace, ventilation is used to control exposure to airborne contaminants. It is commonly used to remove contaminants such as fumes, dust, and vapors, in order to provide a healthy and safe working environment. Ventilation can be accomplished by natural means (e.g., opening a window) or mechanical means (e.g., fans or blowers).

Industrial systems are designed to move out (exhaust) and bring in (intake) a specific amount of air at a specific speed (velocity), which results in the removal of undesirable contaminants. While all ventilation systems follow the same basic principles, each system is designed specifically to match the type of work and the rate of contaminant release at that workplace.

So what is the purpose of an industrial ventilation system?

Introduction to industrial ventilation (1)

Ventilation is considered an “engineering control” to remove or control contaminants released in indoor work environments. It is one of the preferred ways to control employee exposure to air contaminants.

Other ways to control contaminants include:

  • eliminate the use of the hazardous chemical or material,
  • substitute with less toxic chemicals,
  • process change, or
  • work practice change.

The purpose of a ventilation system

There are four purposes of ventilation:

  1. Provide a continuous supply of fresh outside air.
  2. Maintain temperature and humidity at comfortable levels.
  3. Reduce potential fire or explosion hazards.
  4. Remove or dilute airborne contaminants.

The main parts of an industrial ventilation system?

An industrial ventilation system has two main parts: a fresh air supply system and an exhaust system.

In general, the supply system is a heating, ventilation, and air-conditioning system (HVAC) and consists of:


  • air inlet,
  • air filtering equipment,
  • heating/cooling equipment,
  • fan,
  • ducts,
  • air distribution registers.

The exhaust system consists of:

  • an “air intake” area,
  • ducts to move air from one area to another,
  • air cleaning device(s),
  • fan(s) to bring in outside air and exhaust the indoor contaminated air, and
  • discharge stacks.

The basic types of ventilation systems

There are two types of mechanical ventilation systems used in industrial settings:

General industrial ventilationreduces the concentration of the air contaminants or controls the amount of heat that accumulates in hot industrial environments, by mixing (diluting) the contaminated air with fresh, clean, uncontaminated air. This ventilation system is also known asdilution ventilation.

Local exhaustventilation captures contaminants at, or very near, the source and exhausts them outside.

The main features of dilution ventilation

Dilution ventilation supplies and exhausts large amounts of air to and from an area or building. It usually involves large exhaust fans placed in the walls or roof of a building.

Dilution ventilation controls pollutants generated at a worksite by ventilating the entire workplace. The use of general ventilation distributes pollutants, to some degree, throughout the entire worksite and could therefore affect persons who are far from the source of contamination.

Dilution ventilation can be made more effective if the exhaust fan is located close to exposed workers and the makeup air is located behind the worker so that the contaminated air is drawn away from the worker’s breathing zone. See Figures 1 to 4 for examples of better ventilation system layouts, and Figure 5 for poor dilution ventilation design.

When used to control chemical pollutants, dilution must be limited to only situations where:

  • the amounts of pollutants generated are not very high,
  • their toxicity is relatively moderate,
  • workers do not carry out their tasks in the immediate vicinity of the source of contamination, and
  • the emission rate of contaminants is relatively uniform.

It is therefore unusual to recommend the use of dilution ventilation for the control of chemical substances except in the case of solvents that have admissible exposure concentrations of more than 100 parts per million.

Introduction to industrial ventilation (2)
Introduction to industrial ventilation (3)
(Video) Industrial ventilation: a practical overview
Introduction to industrial ventilation (4)
Introduction to industrial ventilation (5)
Introduction to industrial ventilation (6)

Figures 1 to 4: Examples of recommended dilution ventilation layouts
Figure 5: Example of not recommended dilution ventilation layout

The limitations of dilution ventilation

As a method for protecting workers, it is important to know that dilution ventilation:

  • Does not completely remove contaminants.
  • Cannot be used for highly toxic chemicals.
  • Is not effective for dusts or metal fumes or large amounts of gases or vapours.
  • Requires large amounts of makeup air to be heated or cooled.
  • Is not effective for handling surges of gases or vapours or irregular emissions.

Regular “floor” or “desk” fans are also sometimes used as a method of ventilation, but these fans typically blow the contaminant around the work area without effectively controlling it. Opening doors or windows can be used as dilution ventilation, but again, this method is not reliable since air movement is not controlled.

As a general note, the air or “volumetric” flow rate of dilution ventilation depends largely on how fast the contaminant enters the air as well as the efficiency of the fresh air and workroom air mixing process.

The local exhaust ventilation

A local exhaust system is used to control air contaminants by trapping them at or near the source, in contrast to dilution ventilation which lets the contaminant spread throughout the workplace. Local exhaust is generally a far more effective way of controlling highly toxic contaminants before they reach the workers’ breathing zones. This type of system is usually the preferred control method if:

  • Air contaminants pose serious health risk.
  • Large amounts of dusts or fumes are generated.
  • Increased heating costs from ventilation in cold weather are a concern.
  • Emission sources are few in number.
  • Emission sources are near the workers’ breathing zones.

In a general way, a local exhaust system operates similar to a household vacuum cleaner with the hose as close as possible to the place where dirt would be created. ( read more: )

(Video) Industrial Ventilation Part 1

The components of local exhaust ventilation?

A local exhaust system has five basic elements (see Figure 6):

  • The “hood” or opening that captures the contaminant at the source.
  • Ducts that transport the airborne chemicals through the system (exhaust air) and the air that is recirculated.
  • An air cleaning device that removes the contaminant from the moving air in the system (not always required).
  • Fans that move the air through the system and discharges the exhaust air outdoors.
  • An exhaust stack through which the contaminated air is discharged.
Introduction to industrial ventilation (7)

How do I know which type of ventilation system is best for my workplace?

All industrial ventilation systems, when designed properly, should be able to provide long-term worker protection. The two types of ventilation, dilution, and local exhaust, are compared in the following table.

Comparison of Ventilation Systems
Dilution Ventilation Local Exhaust Ventilation
Advantages Disadvantages Advantages Disadvantages
Usually lower equipment and installation costs. Does not completely remove contaminants. Captures contaminant at source and removes it from the workplace. Higher cost for design, installation and equipment.
Requires less maintenance. Cannot be used for highly toxic chemicals. The only choice for highly toxic airborne chemicals. Requires regular cleaning, inspection and maintenance.
Effective control for small amounts of low toxicity chemicals. Ineffective for dusts or metal fumes or large amounts of gases or vapours. Can handle many types of contaminants including dusts and metal fumes.
Effective control for flammable or combustible gases or vapours. Requires large amounts of heated or cooled makeup air. Requires smaller amount of makeup air since smaller amounts of air are being exhausted.
Best ventilation for mobile or dispersed contaminant sources. Ineffective for handling surges of gases or vapours or irregular emissions. Less energy costs since there is less makeup air to heat or cool.

The limitations of any ventilation system

Some limitations include:

  • The systems deteriorate over the years because of contaminant build-up within the system, especially filters.
  • Require ongoing maintenance.
  • Regular and routine testing is needed to identify problems early and implement corrective measures.
  • Only qualified persons should make modifications to a ventilation system to make sure the system continues to work effectively.

The following is an example of changes that can affect how a system works:

Introduction to industrial ventilation (8)

Addition of an exhaust duct branch

When an additional exhaust branch is added to an existing duct the local exhaust ventilation will pull air into the system from the new location. This will reduce the airflow from other locations that are further away from the exhaust fan. The airflow through the entire ventilation system will be affected. This change will result in a rapid plugging of the system and in an exhaust airflow, throughout all ducts, that may not be adequate enough to remove the contaminants.

What should I know about make-up air?

An important and sometimes overlooked aspect of local ventilation is the need to provide enough air to replace the air that is exhausted from the workplace. If enough make-up air is not provided when large volumes of air are exhausted, the workplace becomes “starved” for air and negative pressure is created.

Negative pressure in the workplace increases resistance on the ventilation system causing it to move less air. Air will also enter a building through cracks around doors or windows or other small openings to try to “equal” the rate of air being removed. The result is that workers may be exposed to cold air in the winter, and additional heating costs may occur.

One way to figure out if a room is under negative pressure is to open the door about 3 millimeters and hold a smoke tube (or another object that releases smoke) in front of the opening. If the smoke is drawn into the room, the room is under negative pressure. If the smoke is pushed away from the room, the room is under positive pressure. If the smoke rises straight into the air, then the pressure in the room is the same as the outside pressure.

(Video) Industrial Ventilation part 1

Another way to judge if a building is under excessive negative pressure is to open a door that pushes towards the outside. If you have to pull (or push from inside) hard to open the door, the building is under negative pressure (the outside pressure is higher than inside, and forces the door shut).

( Photo of the day: Indoor Air Quality )

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What are the 3 types of ventilation? ›

There are three methods that may be used to ventilate a building: natural, mechanical and hybrid (mixed-mode) ventilation.

What is ventilation in industry? ›

What is industrial ventilation? Ventilation is the mechanical system in a building that brings in "fresh" outdoor air and removes the "contaminated" indoor air. In a workplace, ventilation is used to control exposure to airborne contaminants.

What are the main points for ventilation? ›

Each building ventilation system has three fundamental elements:
  • Ventilation rate: The amount of outside air supplied into space and the outside air quality. ...
  • Airflow direction: The whole airflow direction. ...
  • Airflow pattern: Airflow pattern or air distribution.
25 Oct 2020

What are the components of an industrial ventilation system? ›

There are two (2) key components to an industrial ventilation system for a food processing plants: 1) the supplied air needs to be filtered to remove contaminants and 2) there must be a positive pressure – this is so that when a door is opened the inside air flows out thus the outside air does not come in.

What are the 2 types of ventilation? ›

The two main types of mechanical ventilation include positive pressure ventilation where air is pushed into the lungs through the airways, and negative pressure ventilation where air is pulled into the lungs.

What are the 4 phases of ventilation? ›

There are four stages of mechanical ventilation. There is the trigger phase, the inspiratory phase, the cycling phase, and the expiratory phase.

What are the types of industrial ventilation? ›

There are three main types of industrial ventilation: Natural Ventilation. Diluting General Ventilation. Exhaust Ventilation.

What is ventilation and its types? ›

There are three types of natural ventilation occurring in buildings: wind driven ventilation, pressure-driven flows, and stack ventilation. The pressures generated by 'the stack effect' rely upon the buoyancy of heated or rising air.

What is ventilation in short answer? ›

Purpose provided (intentional) ventilation: Ventilation is the process by which 'clean' air (normally outdoor air) is intentionally provided to a space and stale air is removed. This may be accomplished by either natural or mechanical means.

What is the process of ventilation? ›

It is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation). Air flows because of pressure differences between the atmosphere and the gases inside the lungs.

What is the importance of ventilation? ›

Proper ventilation keeps the air fresh and healthy indoors. Like the lungs, homes need to be able to breathe to make sure that fresh air comes in and dirty air goes out. Air indoors can build up high levels of moisture, odors, gases, dust, and other air pollutants.

What are the ventilation hazards? ›

What are the harms? Harmful ventilation systems in the workplace create an atmosphere where minimal air movement results in the accumulation of contaminated air, exposing workers to potentially hazardous conditions for the duration of their working day. They may then suffer the health effects beyond the workplace.

What are the instrument used in ventilation? ›

Multi-Function Ventilation Meters. Rotating Vane Anemometer. Hydronic Manometers. Duct Accreditation (PANDA) System.

What is ventilation example? ›

Ventilation refers to the breathing process of a living thing. For example, in humans, pulmonary ventilation is a type of ventilation that takes place between the lungs and the environment. Two main types are pulmonary ventilation and mechanical ventilation.

What is peep in ventilation? ›

DEFINITION. Positive end-expiratory pressure (PEEP) is the alveolar pressure above atmospheric pressure that exists at the end of expiration.

What is the ventilation rate? ›

Ventilation rate is expressed as the volume of gas entering or leaving the lungs in a given amount of time. It can be calculated by multiplying the volume of gas, either inhaled or exhaled, during a breath (the tidal volume) by the breathing rate [e.g., 0.4 liter (or 0.4L) × 15 breaths/min = 6L/min].

What is R and C in ventilator? ›

Simple RC network model of ventilator system and patient, with linear resistance (R v ) and compliance (C v ) for the ventilator tubing system, and linear resistance (R) and compliance (C) for the patient. The RC model calculates tidal volume as a function of variations in patient R and C values.

What are 5 examples of ventilator modes? ›

Other Modes of Mechanical Ventilation
  • Continuous Mandatory Ventilation (CMV)
  • Airway Pressure Release Ventilation (APRV)
  • Mandatory Minute Ventilation (MMV)
  • Inverse Ratio Ventilation (IRV)
  • Pressure Regulated Volume Control (PRVC)
  • Proportional Assist Ventilation (PAV)
  • Adaptive Support Ventilation (ASV)
28 Aug 2022

What is the best type of ventilation? ›

Balanced ventilation.

Much better ventilation is provided through a balanced system in which separate fans drive both inlet and exhaust airflow. This allows us to control where the fresh air comes from, where that fresh air is delivered, and from where exhaust air is drawn.

Which pipe are used for ventilation? ›

A spiral pipe is used for the supply and exhaust of air. This pipe can be used for a MVHR system, mechanical ventilation and natural ventilation. The spiral pipes can be used everywhere in the house.

How do I calculate CFM? ›

To calculate Air Flow in Cubic Feet per Minute (CFM), determine the Flow Velocity in feet per minute, then multiply this figure by the Duct Cross Sectional Area.

What are the three basic steps of human ventilation? ›

Pulmonary ventilation involves three different pressures: Atmospheric pressure. Intraalveolar (intrapulmonary) pressure. Intrapleural pressure.

What is another word for ventilation? ›

Alternate Synonyms for "ventilation":

breathing; external respiration; respiration; bodily process; body process; bodily function; activity.

What is normal ventilation? ›

Definition. Normal ventilation is an automatic, seemingly effortless inspiratory expansion and expiratory contraction of the chest cage. This act of normal breathing has a relatively constant rate and inspiratory volume that together constitute normal respiratory rhythm.

What are the 5 main functions of the lungs? ›

Warms air to match your body temperature and moisturizes it to the humidity level your body needs. Delivers oxygen to the cells in your body. Removes waste gases, including carbon dioxide, from the body when you exhale. Protects your airways from harmful substances and irritants.

What are the 5 steps of inhalation? ›

Use your inhalation chamber effectively in 5 steps
  • Remove the caps and shake the inhaler. ...
  • Purge and insert the mouthpiece into the inhaler. ...
  • Place the mouthpiece or mask correctly. ...
  • Release a dose of the medicament. ...
  • Wait !
2 Jul 2018

What are the 7 steps of inhalation? ›

Terms in this set (7)
  • Your diaphragm moves down as it contracts. ...
  • Air rushes in through the nose and mouth and passes through the throat. ...
  • Air moves into your bronchi. ...
  • Air moves into your alveoli. ...
  • Carbon dioxide moves from the blood through the walls of capillaries and alveoli in order to be expelled by the lungs.


1. Elements of Ventilation Systems
(METPHAST Program)
2. OSHA! A Practical Overview: Industrial Ventilation
(Marvelous Movies)
3. Introduction to Local Exhaust Ventilation
(Institution of Mechanical Engineers - IMechE)
4. Industrial Ventilation 1
(Thesdha USA)
5. Industrial ventilation system
6. What Are the Different Types of Industrial Ventilation?
(werlerd mwerar)
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