Stairwell Vent Kits

Inline box fans are engineered to deliver high-performance ventilation with integrated acoustic attenuation, making them ideal for schools, offices, hospitals and residential projects where quiet operation is a priority. Housed in insulated casings, they reduce sound transmission without compromising airflow performance, ensuring a balance of comfort and efficiency in noise-sensitive environments. Contractors value their modular design and ease of installation, with units often compatible with building management systems (BMS) and capable of fulfilling general ventilation duties.

Certain ranges are available with certification to BS EN 12101-3, enabling their use in emergency smoke extract systems where specified. Inline box fans are tested to BS EN ISO 5801 (Performance testing of fans) and BS EN ISO 5136 (Acoustics – Sound power radiated into ducts), ensuring accurate airflow, pressure and noise performance. For the UK market, they support compliance with Approved Document F (Ventilation) and Approved Document L (Conservation of Fuel and Power), alongside adherence to the Ecodesign Regulation (EU 327/2011, retained in GB law), which enforces strict minimum efficiency requirements. Energy efficiency is enhanced through the use of EC motors, high-efficiency IE3/IE4 induction motors, and VSD-compatible controls, allowing airflow to be adjusted based on occupancy. This supports compliance with Part L of the Building Regulations and helps projects achieve BREEAM and LEED sustainability targets. By combining low-noise performance, robust compliance, and energy-efficient design, inline box fans provide a reliable, scalable solution for modern ventilation systems.

Engineers must confirm each fan has a dedicated, lockable local isolator in an accessible position. Isolation should not disable unrelated systems, and details should be shown on drawings to ensure safe lock-off and maintenance procedures.

Contractors should build O&M records progressively, capturing test results, airflow setpoints, wiring diagrams, acoustic treatments, and as-built modifications. This avoids reliance on generic documents and ensures records match the installed system.

Commissioning should follow CIBSE Commissioning Codes, BSRIA BG 49/2015, and manufacturer instructions. For fans intended as smoke extract units, compliance with BS EN 12101-3 must be evidenced via certification and documentation. On-site checks verify operation under emergency mode but do not replicate laboratory fire testing.

This answer references a standard(s) that are relevant. There may however be many other standards that need to be considered. We recommend you refer to our technical bulletins for more detailed references to applicable standards but also you should check with your professional consultants and the approving authorities prior to purchasing to check compliance.

Please see the Technical Bulletin for more information.

Typical errors include:
• Selecting uncertified fans.
• Failing to keep certificates or Declaration of Performance (DoP).
• Installing outside the certified orientation or accessories.
• Omitting verification of emergency operation during commissioning.
• This answer references a standard(s) that are relevant. There may however be many other standards that need to be considered. We recommend you refer to our technical bulletins for more detailed references to applicable standards but also you should check with your professional consultants and the approving authorities prior to purchasing to check compliance.

Please see the Technical Bulletin for more information.  

Duty point checks confirm the fan achieves the specified airflow and pressure. Without verification, systems may underperform, operate inefficiently, or fail compliance checks, causing disputes and delays in sign-off.

O&M documentation should include design versus measured airflows, damper settings, fan speed, and motor current. These records form the baseline for maintenance and performance comparison over the asset life.

Fans are usually integrated with the BMS via volt-free contacts or digital protocols such as Modbus/BACnet. Retrofit works often require adapting signals to legacy systems, with compatibility and alarm functions verified during commissioning and logged in O&M manuals.

Constraints include limited ceiling void or plantroom space, inadequate structural support for vibration isolators, and restricted access for installation or servicing. Poor planning can cause excessive noise, vibration breakout, and higher maintenance costs.

First, check duct connections and flexible joints for leaks or misalignment. Confirm silencers are the correct size and installed properly. If noise persists, review fan speed and duty point, as operating off-curve often increases noise. In sensitive spaces, additional silencers or acoustic lining may be required.

Fans must be sized to account for clean and dirty filter resistance. Differential pressure sensors should monitor filter blockage, and alarms should alert the BMS when replacement is required. This prevents motor strain and ensures continued safe operation.

Inline box fans are rectangular or cubic cased fans designed to fit within ductwork. They combine strong airflow performance with acoustic lining inside the casing, making them ideal where space is limited and low noise is critical.

Yes, if the model is designed for external use. Outdoor fans must have weatherproof, IP-rated casings and accessories, with installation following manufacturer guidance to prevent water ingress and protect controls.

Routine maintenance includes cleaning, inspection of duct connections, and checking filter condition. Where applicable, bearings should be lubricated — although many modern EC fans use sealed-for-life bearings requiring minimal attention. Regular checks should also confirm correct motor operation and vibration isolation.