System Explanation

Ductwork refers to the system of ducts used to transport air from heating, ventilation, and air-conditioning (HVAC) equipment throughout a building. Properly installed and well-maintained air ducts are a key component of indoor air quality and home comfort.

The Building Regulations require all enclosed workspaces be ventilated by either natural or mechanical means. The following are some of the factors that determine the ventilation requirements of a workspace:

• Human habitation (minimum fresh-air requirement).
• Thermal comfort.
• The activities of the department, that is, extraction of odours, aerosols, gases, vapours, fumes, and dust - some of which may be toxic, infectious, corrosive, flammable, or otherwise hazardous.
• The removal of heat generated by equipment. For example, catering, wash-up, sterilizing areas, electrical switch rooms, and some laboratory areas.
• The reduction of the effects of solar heat gains.
• The reduction of excessive moisture levels to prevent condensation. For example, in hydrotherapy pools.
• Combustion requirements for fuel burning appliances.

Duct design involves planning, sizing, optimising, and detailing. Duct sizes are calculated based on the relationship between air volume, size, air velocity and resistance.

Materials

Ducts can be fabricated from a range of materials but the most typical are the below:

Galvanised

• This sheet metal option for HVAC ductwork is based on galvanized mild steel with a rust-resistant zinc coating.
• This is the most common material used as the zinc coating prevents rust forming.
• This is the most common material used as the zinc coating prevents rust forming.

Aluminium

• This is lightweight and quick to install.
• Custom shapes can be easily fabricated as required by the particular design.
• One of aluminum's notable qualities is its propensity to resist rust, allowing for a longer service life.
• This type of duct can be used in areas prone to moisture like pool areas.

Fibreglass

• -This provides built-in thermal insulation and sound is absorbed by the interior surface.
• -Its lining is well-insulated, reducing heat loss as it travels through the ducts.
• -This material is very popular in commercial buildings.
• -You just must be careful when handling fiberglass ductwork materials because they require intense cleaning that

Flexible duct

• -Flexible ducts are made with wire and plastic polymer.
• -They’re basically flexible steel coils covered in thick plastic.
• -Flexible ducts are cheaper compared to the other three options and are easier to install than rigid ducts.
• -These are normally installed to connect rigid (galvanized, Al etc.) duct to Grill faces.

Prefabricated

• This type of duct is built and tested off-site.
• When it is delivered to the site, it is quite easy to assemble and install.
• It comes pre-insulated and with pre made access doors.
• Note: the prefab ductwork shown in the photo is an AHU (Air Handling Unit) but note that prefab duct has a similar look and structure as per the AHU in the photo.

Ventilation System Typical Equipment and Components

Air Handling Unit (AHU)

An Air Handling Unit (AHU) is the composition of elements mounted in modules (large, accessible box-shaped units), which house the appropriate ventilation requirements for purifying, air-conditioning, or renewing the indoor air in a building or premises.

They are installed in the Plant Rooms, which normally are on the roof of buildings, and through ducts, the air is circulated to reach each of the rooms in the building in question.

See below an example on how the air is circulating from the AHUs to the different areas through the risers. The AHUs act as vital hubs in this process, channelling air through a network of ducts that traverse the building's structure.

These ducts serve a dual purpose: they may supply air to larger zones or cater to individual rooms, contingent upon the intended design objectives.

As an example, in specialized environments like hospitals, a meticulous approach is taken. Dedicated AHUs are allocated for specific isolation rooms, ensuring an elevated state of air quality control. This strategy limits the duct's scope to a single isolation room, a deliberate choice driven by the need to shield vulnerable patients from potential airborne contaminants. The rationale behind this approach is clear: the health of patients is paramount, necessitating an airtight system that prevents pollutants from circulating back to the AHU. The potential ramifications of a breach along this path is quite important - a breach could facilitate the spread of illness through the air.

The way ducts are designed and set up from AHUs is a careful balance between efficiency and health concerns. For instance, the specific design for hospital isolation rooms highlights the main idea: designs that focus on keeping people healthy while reducing the chance of airborne infections. This shows how ventilation systems are essential for creating a safe and comfortable indoor environment.

The purpose of the AHU is:

• Control and filtering on the quality air.
• Control of the temperature that regulates the system of air conditioning whether it is hot or cold to ensure that the thermal sensation inside the room is satisfied.
• Monitoring relative humidity for better indoor comfort.

How is the AHU composed:

• Air intake: air handling units collect air from outside, which is treated and distributed throughout the rooms; and/or indoor air that is "recycled".
• Filter: depending on the air purity requirements, the filter applied will have a higher or lower particle, viruses, bacteria, odours, and other air pollutants retention.
• Fan: this is an electromechanical system that powers the air to expel it from the AHU to the ducts that distribute the air throughout the rooms.
• Heat exchangers: devices that transfer temperature between two fluids, in this case, coolant and air, separated by a solid barrier.
• Cooling coil: the air passing through this module is cooled. In this process, water droplets can be generated, which are collected in a condensate tray thanks to the built-in droplet separator.
• Silencer: coatings that considerably reduce the sound level of the installation.
• Plenums: empty spaces in which the air flow is homogenised.

In short:

• AHUs take fresh ambient air from outside, clean it, heat it or cool it, maybe humidify it and then force it through some ductwork around to the designed areas within a building.
• Most units will have an additional duct run to then pull the used dirty air out of the rooms, back to the AHU, where a fan will discharge it back to atmosphere.
• Some of this return air might be recirculated back into the fresh air supply to save energy.

Attenuators

Duct attenuators, also known as sound attenuators or noise silencers, are devices used in ventilation systems to reduce the noise generated by the airflow within ductwork. They are designed to absorb and dampen sound waves, helping to create a quieter and more comfortable indoor environment.

In simple terms, in the ventilation systems, air moves through ducts to keep comfort. Sometimes, this moving air can make noise. Attenuators are like special sections in the ducts that have this sound-absorbing material inside them.

Duct attenuators serve two primary functions:

• Noise Reduction: As air flows through ductwork, it can create noise due to turbulence, friction, and other factors. Duct attenuators contain sound-absorbing materials that capture and dissipate the energy of these sound waves, effectively reducing the noise levels transmitted through the duct system.
• Airflow Equalization: In some cases, duct attenuators are designed with internal configurations that help balance the airflow distribution within the ducts. This can contribute to improved air distribution and performance of the ventilation system.

Duct attenuators are typically installed within the ductwork itself. They are positioned at specific points where noise reduction is desired, such as near noisy equipment (fans or air handling units), in areas close to occupied spaces, or where airflow velocities are high and noise levels are likely to be elevated.

NOTE:

Duct attenuators serve the dual purpose of noise reduction and, to some extent, contributing to airflow balance where needed. In situations demanding both noise reduction and precise airflow control, a combination of duct attenuators and Volume Control Dampers (VCDs) is often employed. In the following section, we will look at VCDs, which primarily function to provide precise control over airflow distribution.

Fan Coil Unit (FCU)

• FCUs are usually smaller units (compared to AHUs) placed within individual rooms or spaces. They also help control air temperature, but they're more localized.
• FCUs have their own built-in fan and coil system.
• While they might not be directly connected to the ductwork of the AHU, they can have their own supply air intake. This intake allows the FCU to pull in air from the room, pass it through its coils to adjust the temperature, and then blow the conditioned air back into the same room.
• The FCU heat output is controlled using a control valve linked to the room via a thermostat. This in turn would be connected to a Building Management System (BMS), which controls the throughput of water to the heat exchanger.

Mechanical Ventilation with Heat Recovery (MVHR)

It is a type of ventilation system used in buildings to provide controlled and efficient fresh air exchange while also recovering heat from the extracted stale air (indoor air that has become depleted or contaminated due to the accumulation of various pollutants, odors, moisture, and potentially harmful substances).

MVHR systems are designed to enhance indoor air quality and energy efficiency by minimizing heat loss and reducing the need for additional heating or cooling.

In an MVHR system, the process generally involves the following steps:

• Supply and Exhaust: Fresh outdoor air is drawn into the building through supply vents and distributed to living spaces. At the same time, indoor air is extracted from areas like kitchens, bathrooms, and utility rooms through exhaust vents.
• Heat Recovery: Within the MVHR unit, the incoming fresh air and the outgoing stale air pass through separate heat exchangers, which can recover as much as 90% of the heat in this air that would typically be lost in traditional means of ventilation. Heat is transferred from the warm, outgoing air to the cooler, incoming air without the two airstreams mixing. This process helps to preheat the fresh incoming air, reducing the amount of additional heating required to maintain indoor comfort.
• Air Filtration: The incoming air is typically filtered to remove dust, pollen, and other particles, contributing to improved indoor air quality.
• Distribution: The preheated and filtered fresh air is then distributed to various rooms and spaces, while the extracted stale air is expelled to the outside

MVHR systems are particularly beneficial in energy-efficient buildings, well-insulated homes, or areas with stringent ventilation requirements. They help minimize heat loss during ventilation, reduce energy consumption, and maintain a consistent supply of fresh air. These systems are commonly used in residential, commercial, and institutional buildings to promote occupant comfort, health, and energy savings.

• Fresh Air: Fresh air refers to the outdoor air that is brought into the building to provide ventilation and maintain a healthy indoor environment. Fresh air is typically filtered to remove particles and contaminants before being introduced into the living spaces.
• Exhaust Air: Exhaust air is the indoor air that is extracted or removed from the building. This air may contain pollutants, odors, and excess humidity. The exhaust air is expelled to the outside of the building.
• Supply Air: Supply air is the filtered and conditioned outdoor air that is supplied or introduced into the living spaces of the building. This air helps maintain indoor air quality, provides oxygen for occupants, and contributes to a comfortable environment.
• Extract Air: Extract air is the indoor air that has been extracted from the building and is ready to be expelled to the outside. It has passed through the heat recovery process where its heat (energy) is transferred to the supply air before being discharged.

Volume Control Damper (VCD)

• A VCD is a specific type of damper used to control the flow of air in an HVAC heating or cooling system.
• Unlike fire dampers that are installed within walls, VCDs are integral components of the ductwork system. They find their placement at various points along the branching network, precisely where the need arises to manage and direct the flow of air as indicated in the drawing below.
• Circular VCDs are normally referred to Iris dampers.

MFSD (Mechanical Fire Smoke Dampers)

Fire dampers are installed in fire rated walls and floors, at the point of duct penetration, to retain the integrity and fire rating of a wall or floor whether it is a ducted or open plenum return application. Should the ductwork fall away, the damper needs to stay in the wall or floor to maintain the integrity of the wall or floor. One should actually think of the fire damper as part of the wall system itself.

A fire damper is a mechanical device installed in ducts crossing fire rated walls.

• These devices are designed to close automatically upon detection of heat or/and smoke.
• Its primary function is to prevent the passage of flame and smoke from one side of a fire-rated separation to the other.
• They serve to interrupt migratory airflow, the passage of flame, and maintain the integrity of the fire rated separation.
• The installation of life/safety dampers should always be accomplished in accordance with the manufacturer’s instructions. Installation instructions provided by a manufacturer should never be used to install the dampers of a different manufacturer as the dampers may not have been tested to and passed the specific installation.

Pressure Stabilizers (PS)

"Wall mounted" or "ceiling mounted" pressure stabilizers refer to devices that are installed on walls or ceilings to help maintain a specific pressure relationship between two adjacent spaces.

These devices are commonly used in controlled environments where pressure differentials are crucial, such as in cleanrooms, laboratories, isolation rooms, or areas with specific air quality requirements.

In the context of isolation rooms with airlocks/ante rooms:

• A pressure stabilizer may be used to maintain positive pressure within the isolation room, preventing airborne contaminants from escaping.
• The airlock, which serves as a buffer zone between the isolation room and the outside environment, helps maintain the pressure differential and minimizes the risk of contamination spreading to other areas.
• These devices typically include sensors that monitor the pressure levels in the two spaces and control mechanisms that adjust dampers or airflow rates to maintain the desired pressure differential.
• Wall-mounted or ceiling-mounted pressure stabilizers are essential components in creating and maintaining controlled environments where air quality, contamination prevention, and pressure differentials are critical factors.

What does it mean to maintain pressure differentials, positive pressure, or negative pressure?

• Maintaining pressure differentials refers to the deliberate control and management of air pressure variations between different spaces within a building or facility.
• It involves creating specific pressure relationships between areas to achieve desired outcomes such as contamination control, airflow direction, or comfort.
• Pressure differentials are typically achieved by controlling the volume of air being supplied or extracted from various spaces.

There are two main types of pressure differentials:

Positive Pressure:

• In a positive pressure environment, the air pressure within a room or space is higher than that in its surrounding areas.
• This means that air tends to flow out of the positively pressurized space and prevent contaminants from entering.
• Positive pressure is often used in clean rooms, operating rooms, and isolation rooms to maintain a controlled and contamination-free environment.

Negative Pressure:

• In a negative pressure environment, the air pressure within a room or space is lower than that in its surroundings.
• This causes air to be drawn into the negatively pressurized space, containing contaminants within that space, and preventing them from spreading to other areas.
• Negative pressure is commonly used in spaces where hazardous materials, fumes, or airborne pathogens need to be contained, such as laboratories or quarantine areas.

Maintaining pressure differentials is crucial for various reasons:

• Contamination Control: Proper pressure differentials prevent the migration of contaminants, particles, or pathogens from one area to another, ensuring a clean and controlled environment.
• Infection Control: In healthcare settings, pressure differentials help prevent the spread of airborne infections by containing contaminated air within specific isolation rooms.
• Product Quality: Industries such as pharmaceuticals and electronics manufacturing rely on pressure differentials to maintain the cleanliness and quality of products.
• Safety: Negative pressure ensures the safety of personnel by containing hazardous substances or pathogens within controlled spaces.
• Process Control: Pressure differentials control the direction of airflow, facilitating specific processes and preventing cross-contamination.
• Energy Efficiency: Proper pressure differentials help optimize ventilation and airflow, contributing to energy-efficient building operations.

In summary, maintaining pressure differentials involves creating controlled airflows that direct air from higher-pressure areas to lower-pressure areas or vice versa. This controlled airflow serves various critical purposes in ensuring contamination control, safety, product quality, and overall environmental performance.

Transfer Grilles (TG)

Wall-mounted or door-mounted transfer grilles are ventilation components used to facilitate the movement of air between two adjacent spaces, typically for the purpose of maintaining pressure differentials or promoting airflow in various building environments. These grilles are designed to allow controlled airflow while preventing the transfer of contaminants, odours, or noise between the spaces.

Wall-Mounted Transfer Grilles:

• Wall-mounted transfer grilles are installed on walls or partitions separating two rooms or zones.
• They provide a pathway for air to flow from one space to another, helping to equalize pressure, temperature, or air quality between the areas.
• These grilles often include adjustable louvers or dampers that allow for fine-tuning the airflow rate.
• They are commonly used in situations where maintaining consistent air pressure or airflow is important, such as between cleanrooms and adjacent areas, or between rooms with different ventilation requirements.

Door-Mounted Transfer Grilles:

• Door-mounted transfer grilles are installed within doors, either at the top, bottom, or on the sides, to allow airflow between rooms that have different pressure levels or environmental conditions. These grilles are especially useful in applications where maintaining a specific pressure relationship is crucial, such as in isolation rooms, operating rooms, or laboratories. By installing transfer grilles in doors, air can move between rooms while minimizing the risk of contaminant transfer or compromising pressure differentials.
• Both wall-mounted and door-mounted transfer grilles play a role in achieving balanced air distribution and controlled airflow within a building, ensuring that different spaces maintain the desired conditions while preventing the spread of pollutants or unwanted elements. These grilles are essential components in creating a comfortable, safe, and energy-efficient indoor environment.

NOTE:

Pressure stabilizers are employed when maintaining specific pressure relationships is crucial for safety, contamination control, or system performance, while Transfer Grilles are utilized when controlled airflow between spaces is desired without the same level of pressure differential management.

Air terminals/Grilles

Air terminals are integral components of HVAC systems that serve as the end points through which conditioned air is delivered to or extracted from a building's indoor spaces.

They play a crucial role in ensuring effective air distribution, maintaining comfort, and achieving desired indoor air quality levels. Air terminals are strategically designed and placed to optimize airflow, temperature, and humidity control throughout various zones of a building.

There are different types of air terminals, each serving a specific function within the HVAC system, like diffusers, grilles, jet diffusers, displacement diffusers etc.

The most common ones you would recognize are the diffusers. These disperse conditioned air into a room in a controlled and uniform manner. They help ensure even air distribution, minimize drafts, and promote comfort for occupants. Diffusers come in various designs, including ceiling diffusers, floor diffusers, and wall-mounted diffusers.

Parts of a Ductwork System

Ductwork Plenum

The plenum is a key element in the design and layout of ductwork, acting as a central hub for the distribution of air to various zones or rooms within the building.

The plenum is usually located at the point where the air handler is connected to the ductwork.

In a forced-air heating system, the Plenum also serves as the collecting point for all the return air from the house. This return air passes through the plenum and is then sent back to the air handler to be reheated and redistributed.

The primary functions of a ductwork plenum include:

• Air Mixing: The plenum allows air from different sources, to mix before being distributed to various areas. This helps ensure a consistent and balanced supply of conditioned air.
• Pressure Equalization: The plenum helps equalize air pressure across different branches of the ductwork, ensuring that airflow is evenly distributed to all parts of the building.
• Transition Point: The plenum serves as a transition point between the larger main ducts and the smaller distribution ducts that deliver air to specific rooms or zones.

NOTE:

The term "plenum" can also refer to the space above a suspended ceiling or below a raised floor, where return air is collected before being drawn back into the HVAC system. In this context, the plenum helps manage the return airflow and contributes to maintaining the desired indoor air quality.

Ductwork boots

• Ductwork boots serve as markers guiding the airflow within HVAC
• systems.
• Proper installation of boots aligns with the intended direction of air
• movement.
• These components ensure efficient and balanced air distribution throughout ductwork. Alignment and placement of boots impact the overall effectiveness of the HVAC system.

Elbows and Turning Vanes

• Turning vanes are installed to redirect air flow in square elbow fittings.
• Turning vanes are placed internally at the points where direction changes.
• They serve as the “wind breakers” of the duct system.
• They help reduce the pressure or turbulence caused by an approaching air flow.
• Due to their circular cross-section, spiral ducts have a natural tendency to direct airflow smoothly along their curves, without the abrupt changes in direction that can lead to turbulence and pressure loss, reason why these don’t have turning vanes.

Cleats and Flange Clamps

• Cleats and flange clamps reinforce ductwork joints, ensuring stability and preventing air leakage.
• They maintain airtight connections, support pressure differentials, and absorb vibrations.
• By securing duct sections tightly, they enhance energy efficiency and indoor air quality.

Seals and Gaskets:

These ensure airtight connections at joints and openings to prevent air leakage and maintain energy efficiency.

Seals and gaskets are strategically placed in various locations within HVAC systems to ensure effective performance and energy efficiency:

• Duct Joints.
• Access Doors.
• Equipment connections.
• Dampers.

Take-offs

A duct take-off is a branching point in HVAC ductwork where a smaller duct diverts from the main duct. It directs a portion of conditioned air to a specific area, room, or supply register, allowing for efficient distribution throughout the building.

NOTE:

HETO stands for High Efficiency Take Off.

Reducers

Reducers are components that transition between ducts of different sizes. They gradually decrease or increase the duct size to accommodate changes in airflow volume or to connect ducts of different dimensions, ensuring smooth and efficient airflow while minimizing pressure losses.

Access doors

Access doors (ADs) in ductwork are openings that allow entry for inspection, cleaning, and maintenance of HVAC systems. They are typically hinged, or removable panels installed along ducts. Access doors play a vital role in ensuring system hygiene, as recommended by standards like TR19. TR19 provides guidelines for duct cleanliness and maintenance, specifying the size of access doors required based on the size of the duct.

Ductwork

Typical layout

Duct Specs

Ventilation systems are key to making indoor spaces comfortable, keeping the air clean, and saving energy. Specific rules are created to design, install, and take care of the duct systems. These rules, known as duct specifications, focus on different parts of ducts and ventilation.

DW 143 Ductwork Leakage Testing:

• -DW 143 sets out procedures for testing the leakage of ductwork systems to ensure they meet specific performance standards.

DW 144 Ductwork:

• DW 144 provides guidelines for the construction and installation of ductwork systems.
• It covers aspects like design, materials, fabrication, and installation methods to ensure ductwork is efficient, safe, and compliant.

DW 145 Fire Dampers:

• DW 145 focuses on fire dampers, which are crucial safety components that help prevent the spread of fire through HVAC systems.
• The standard addresses their design, installation, testing, and maintenance requirements.

DW 154 Plastic Ductwork:

• DW 154 offers guidance on the use of plastic materials in ductwork construction.
• It covers material selection, fabrication, installation, and safety considerations related to plastic ductwork systems.

DW 172 Kitchen Ventilation:

• DW 172 outlines standards for kitchen ventilation systems, addressing design, installation, and maintenance to ensure effective removal of cooking fumes, odors, and pollutants from commercial kitchens.

TR19 Ventilation Cleanliness Internal:

• TR19 provides industry recommendations for the cleanliness and hygiene of ventilation systems.
• It emphasizes regular inspection, cleaning, and maintenance to ensure optimal indoor air quality and system efficiency.

Fire Compartments

Compartmentation involves dividing a building into separate sections to manage risks effectively. Each section, or compartment, is made strong with fire-resistant materials and safety features like fire doors and cavity barriers.

• Fire compartments are like safety zones in buildings. They keep fires contained, giving people more time to escape and firefighters more time to put out the fire.
• In places like schools, people can usually move quickly during a fire. But in hospitals, where patients can't move easily, fire compartments keep them safe. Data centres also use compartments to protect servers by using fire-resistant walls.
• So, in places where escape might be harder or valuable things need protection, fire compartments are crucial for safety.

The primary objective of compartmentation within buildings is:

• To prevent rapid fire spread which could trap occupants of the building.
• To reduce the chance of fires becoming large on the basis that large fires are more dangerous, not only to building occupants and fire service personnel, but to people in the vicinity of the building.

The provided images illustrate the critical significance of effective fire protection measures when it comes to penetrations such as pipes or containment systems passing through fire-rated walls. In these scenarios, we can see the importance of the fire stopping as it acts as a safeguard against the potential spread of fire and smoke through cavities and openings.

A sticker must be always placed by the fire stopper next to the ope sealing/fire stopping. This typically contains essential information about the fire protection installation. These stickers serve as quick references for building occupants, maintenance personnel, inspectors, and emergency responders. Stickers commonly include the following information:

1. Installer Information: The name, contact details, and certification of the company or individual responsible for installing the fire stopper. This helps in identifying the responsible party for any inquiries or follow-ups.
2. Date of Installation: The date on which the fire stopper was installed. This aids in tracking maintenance schedules and ensuring compliance with safety regulations.
3. Product Information: Details about the specific fire stopper product used, including its brand, model, and specifications. This ensures that the right product was utilized and facilitates future maintenance or replacement.
4. Certification and Compliance: Any relevant certification marks, standards, or codes that the fire stopper complies with. This provides reassurance that the installation meets industry safety standards.
5. Fire Rating: The fire rating of the assembly or barrier in which the fire stopper is placed. This indicates the duration for which the fire barrier can withstand heat and flames.

Inspection and Maintenance: Guidance on regular inspection and maintenance requirements for the fire stopper. This helps ensure ongoing effectiveness and compliance over time.

The use of different colours for these stickers is often part of a standardized color-coding system that conveys specific information at a glance. Different colours may be associated with different types of fire protection systems, indicating their purpose or functionality. For example, red might signify fire-rated penetrations, green might indicate emergency exit paths, and blue might denote safety equipment.

The provided illustration demonstrates a crucial aspect of fire safety within a specific room. It visually communicates essential information about the fire ratings assigned to various components, ensuring comprehensive protection during a fire emergency:

Wall Fire Rating (1hour and 2 Hours): The illustration indicates that the walls of the room have a fire rating of 1 hour and 2 hours. This means these walls can withstand the heat and flames of a fire for that duration before they might be compromised.

Mechanical Penetrations Above Ceiling Void: The diagram further highlights the importance of fire protection in mechanical penetrations passing through the ceiling void. This reinforces the significance of properly installed fire-stopping measures to prevent fire spreading within these cavities.

Door Fire Rating: A critical element, the fire-rated door, is also emphasized. The duration indicates how long the door can resist fire, contributing to compartmentalization and allowing occupants valuable time to evacuate safely.

Types of Ductwork Systems

SA - Supply Air:

• Supply air ducts distribute conditioned air from HVAC systems to various spaces within a building, ensuring a comfortable and controlled indoor environment.

RA - Return Air:

• Return air ducts collect and transport used or stale air back to the HVAC system for treatment and recirculation.

EA - Exhaust Air:

• Exhaust air ducts remove air from specific areas, such as restrooms or laboratories, and expel it outside, helping to maintain healthy and odour-free indoor spaces.

EXA - Extract Air Duct:

• Extract air ducts serve specialized purposes, such as isolating contaminated air from specific areas (isolation rooms) or removing odours and grease from kitchen areas.

SEA - Exhaust Air Smoke:

• Exhaust air smoke ducts are designed to handle smoke and fumes in case of a fire, helping to safeguard occupants and prevent fire spread.

OA - Outside Air:

• Often referred as fresh air intake ducts introduce outdoor air into the building to improve indoor air quality, ensuring a constant supply of oxygen and diluting pollutants.

NOTE:

Some Extraction Ducts are used to:

1. Remove smoke from buildings.
2. Enable emergency evacuation of the occupants.
3. Improve firefighting and flash-over prevention.

They are mainly used in:

1. Large compartments
2. Car parks: the low ceilings present dangerous zones because the smoke layer can fill the space very quickly and prevents evacuation. Sometimes Jet Fans are used as these present more advantages.

https://www.youtube.com/watch?v=izx79YkZRKo

1. High-rise buildings (typically greater than 15 meters): are vulnerable to spreading smoke.
2. Atriums in commercial, office and residential buildings.

Insulation, Cladding and Labels

Insulation of Ductwork:

• Ductwork is often insulated to control temperature, prevent condensation, and enhance energy efficiency.
• Insulation helps maintain the desired temperature of the air inside the ducts, reduces heat loss or gain, and prevents moisture build-up that could lead to corrosion or mould growth.
• Insulated ductwork ensures that conditioned air remains at the desired temperature as it travels through the system, optimizing comfort and system performance.
• In some of the SA duct systems, you will see them installed on top of phenolic blocks, like shown in the image below, to prevent condensation. Note this is project specific.

Cladding of Ductwork:

• Cladding involves covering the exterior of ductwork with protective materials, such as metal or insulation jacketing.
• Cladding provides mechanical protection to ducts, shielding them from physical damage, moisture, and external environmental factors.
• In addition to safeguarding the ducts, cladding can enhance the aesthetics of the space, creating a clean and finished appearance.

Labels on Ductwork:

• Labels on ductwork serve as essential markers that provide information about the system, its purpose, and its specifications.
• Here are some key guidelines for label installation:
  • Regular Intervals: Labels are typically placed at regular intervals along the ductwork. The exact interval may vary based on regulations and project specifications.
  • Visibility Through Access Doors: Labels should be positioned in a way that they remain visible even when ceiling access doors are opened.
  • System Reference: Each label should clearly indicate the system or section it belongs to. This information helps maintenance personnel accurately identify the purpose and location of each duct.
  • Labels After Bends: Labels are often placed after bends, turns, or changes in direction.

NOTE:

In image above we have no information on which system is supplying air to any of the ducts above.

Important Notes:

• The decision to insulate and clad ductwork is often outlined in the Project Technical Specifications. This depends on client preferences, project goals, and specific needs.
• In commercial settings:
  • Insulation is commonly applied to all ductwork installed in plant rooms and risers.
  • In fit-out areas, Supply Air (SA) ducts are insulated to maintain temperature control, while Return Air (RA) ducts may not require insulation.
• Cladding is typically added to ducts installed below 2 meters for protection and safety.
• Ducts located outdoors receive both insulation and cladding to shield them from weather conditions and maintain desired performance.
• Sometimes, ductwork clamps may be left exposed due to project timing. This allows the client to conduct the 1st fix walkdown, ensuring that the duct joints are positioned as per the specifications - usually about 250mm apart from each other.

Process of Installation and offering the system to the client

Ventilation System Offering - Flow Diagram

Ductwork Snagging - Most Typical QA issues

Most common snags in Ventilation systems:

• Brackets
• Access Doors
• Duct Damage
• Insulation and labelling issues

Here some examples of most typical ductwork issues, not necessarily the only issues you might find:

Duct Labelling Typical Issues:

Labels Placement:

• Issue: Labels are not placed at every elbow or regular intervals.
• Consequence: Lack of proper labeling can make it difficult to identify the purpose and direction of the duct.

Label Arrow Direction:

• Issue: Label arrow direction does not indicate the correct airflow direction.
• Consequence: Incorrect arrow direction can lead to confusion about the intended airflow direction of the duct.

Visibility Through Access Hatches:

• Issue: Labels are not installed in locations visible through ceiling access hatches.
• Consequence: Lack of visibility can hinder maintenance and inspection efforts, as well as lead to difficulties in identifying the duct's purpose.

Straight Labels:

• Issue: Labels are not straight.
• Consequence: Crooked labels can appear unprofessional and may be harder to read or interpret.

System Reference Number:

• Issue: System reference number is not indicated next to the arrow label.
• Consequence: Without the system reference number, it's challenging to identify the specific system or section the duct belongs to.