National Ventilation Monsoon MON-DMEVR125HT 125mm Continuous Running Extractor Fan with Humidistat & Timer – IPX5 White

The National Ventilation Monsoon MON-DMEVR125HT is a high-performance 125mm (5-inch) continuous running extractor fan with an integrated humidistat and timer, designed to provide efficient, quiet and reliable ventilation in domestic bathrooms, kitchens and utility rooms.

Part of the Monsoon dMEV R range, this decentralised mechanical extract ventilation fan delivers continuous background airflow to help remove moisture, stale air and indoor pollutants.

Unlike conventional intermittent extractor fans, the MON-DMEVR125HT operates continuously at a low background extraction rate, increasing ventilation automatically when humidity rises or additional extraction is requested.

The built-in digital humidistat incorporates humidity threshold monitoring and rapid-rise detection, making the fan particularly effective in moisture-prone environments such as bathrooms and shower rooms.

The integrated fixed overrun timer with Comfort Mode helps manage boosted extraction before the fan returns to normal background operation.

Designed for low-noise performance, the 125mm Monsoon dMEV R has manufacturer-stated sound levels of 8.5dB(A) at minimum speed, making it suitable for residential installations where quiet continuous ventilation is important.

Its high-pressure, low-noise impeller is designed to deliver effective extraction without requiring a traditional centrifugal fan.

The IPX5 water-resistance rating makes the MON-DMEVR125HT suitable for appropriately installed bathroom Zone 1, 2 and 3 applications.

Designed to support the applicable requirements of UK Building Regulations Part F and Part L, the fan is suitable for new-build properties, refurbishment projects and domestic ventilation upgrades.

With a discreet round white fascia, adjustable airflow settings and wall or ceiling mounting capability, the Monsoon MON-DMEVR125HT provides a practical solution for continuous, humidity-controlled mechanical ventilation.

Key Features

• 125mm (5-inch) continuous running extractor fan

• Integrated digital humidistat – automatic humidity-responsive extraction

• Rapid-rise humidity detection – responds to sudden increases in moisture

• Fixed overrun timer – supports continued extraction following boost activation

• Comfort Mode – integrated ventilation control function

• Continuous background ventilation – helps manage moisture and stale air

• Automatic boost operation – increases airflow when required

• External boost switching capability – additional ventilation control

• Quiet operation – 8.5dB(A) at minimum speed

• High-pressure, low-noise impeller – effective mechanical extraction

• Adjustable airflow settings – supports accurate commissioning

• IPX5 rated – suitable for bathroom Zones 1, 2 and 3 when correctly installed

• 125mm nominal duct connection

• Wall or ceiling mounting

• Round white fascia – clean, discreet appearance

• Designed to support Building Regulations Parts F and L

• Suitable for bathrooms, kitchens and utility rooms

Continuous Mechanical Extract Ventilation

The Monsoon MON-DMEVR125HT is designed to provide continuous background extraction, helping maintain airflow through moisture-prone areas of the home.

Unlike traditional intermittent ventilation, which only operates during selected periods, a dMEV fan runs continuously at a low ventilation rate.

When additional extraction is required, the fan can increase its airflow to help remove excess moisture and stale air.

This makes the MON-DMEVR125HT suitable for modern residential properties where continuous mechanical ventilation forms part of the ventilation strategy.

Automatic Digital Humidistat

The MON-DMEVR125HT features a built-in digital humidity sensor with automatic threshold and rapid-rise detection.

The manufacturer specifies the following humidity response:

• 0–75% relative humidity: background trickle operation

• 76–85% relative humidity: proportional increase between trickle and boost

• 86–100% relative humidity: boost extraction

The rapid-rise detection function also responds when relative humidity increases by more than five percentage points over a five-minute period.

This is particularly useful when showering or bathing causes a sudden increase in moisture levels.

The humidity thresholds are factory preset and are not user-adjustable.

Fixed Timer and Comfort Mode

The Monsoon MON-DMEVR125HT incorporates a fixed overrun timer with Comfort Mode.

This helps manage the fan's boosted extraction cycle following activation, allowing ventilation to continue before returning to its normal continuous background setting.

The combination of humidity-responsive operation and timer control makes the fan suitable for bathrooms where automatic moisture extraction is preferred.

Quiet Running Performance

The Monsoon dMEV R range is engineered for low-noise continuous operation.

For the 125mm model, the manufacturer's technical data specifies:

The low minimum-speed sound level makes the fan suitable for continuous use in domestic environments.

Actual noise levels depend on the selected airflow, ductwork, mounting arrangements and installation conditions.

IPX5 Bathroom Protection

The MON-DMEVR125HT is IPX5 rated, providing protection against water jets.

The manufacturer identifies the Monsoon dMEV R range as suitable for bathroom Zones 1, 2 and 3, subject to correct installation.

This makes it suitable for bathroom and shower-room ventilation projects where an appropriately water-resistant extractor fan is required.

Adjustable Airflow and Commissioning

The Monsoon dMEV R range incorporates adjustable airflow settings, allowing the installer to configure the fan to meet the ventilation requirements of the property.

This is particularly important for continuous mechanical extract ventilation systems, where airflow must be correctly commissioned.

The fan is designed to support compliance with the applicable requirements of Building Regulations Part F and Part L.

Final compliance depends on the complete ventilation design, installation and measured airflow performance.

Suitable Applications

• Domestic bathrooms

• Shower rooms

• En-suite bathrooms

• Kitchens

• Utility rooms

• Toilets and cloakrooms

• New-build residential properties

• Bathroom refurbishment projects

• Domestic ventilation upgrades

• Continuous mechanical extract ventilation installations

• Properties requiring humidity-responsive extraction

Bathroom zone suitability is subject to correct installation, the manufacturer's instructions and applicable electrical regulations.

Frequently Asked Questions

What is the Monsoon MON-DMEVR125HT?

The MON-DMEVR125HT is a 125mm continuous running extractor fan with an integrated humidity sensor and fixed timer, designed for bathrooms, kitchens and utility rooms.

Does the MON-DMEVR125HT run continuously?

Yes. The fan provides continuous background ventilation and increases its extraction rate when additional airflow is required.

Does it have a built-in humidistat?

Yes. The HT model includes an integrated digital humidistat with preset humidity threshold and rapid-rise detection.

Does the fan automatically increase speed when someone showers?

Yes. The humidistat can respond to increased humidity and rapid changes in moisture levels, automatically increasing extraction when the preset conditions are met.

Can the humidity sensitivity be adjusted?

No. The manufacturer specifies preset humidity thresholds that are not user-adjustable.

Does the MON-DMEVR125HT have a timer?

Yes. It includes a fixed overrun timer with Comfort Mode.

How quiet is the MON-DMEVR125HT?

The manufacturer's technical data lists 8.5dB(A) at minimum speed and 37.9dB(A) at maximum speed for the 125mm model.

Is it suitable for bathroom Zone 1?

Yes. The fan is IPX5 rated, and the manufacturer specifies suitability for Zones 1, 2 and 3 when correctly installed.

Can the fan be used in a kitchen?

Yes. The Monsoon dMEV R range is designed for bathrooms, kitchens and utility rooms. The airflow must be commissioned to meet the requirements of the installation.

Can it be ceiling mounted?

Yes. The fan is designed for wall or ceiling mounting in accordance with the manufacturer's instructions.

What size ducting does it use?

The fan is a 125mm nominal model, with a manufacturer-specified spigot diameter of 120mm. Compatible ducting and installation dimensions should be checked before fitting.

What is the difference between MON-DMEVR125 and MON-DMEVR125HT?

The MON-DMEVR125 is the standard 125mm continuous running model without an integrated humidity sensor.

The MON-DMEVR125HT includes an integrated digital humidistat for automatic humidity-responsive ventilation.

Both models belong to the Monsoon dMEV R range.

What is the difference between MON-DMEVR100HT and MON-DMEVR125HT?

The MON-DMEVR100HT is the 100mm version, while the MON-DMEVR125HT is the larger 125mm version.

Both feature continuous ventilation, integrated humidity sensing and fixed timer functionality.

The correct model should be selected according to the ducting arrangement and required ventilation performance.

Installation Information

The National Ventilation Monsoon MON-DMEVR125HT is designed for fixed electrical installation and should be fitted by a suitably competent person.

Installation must follow the manufacturer's instructions and applicable requirements of BS 7671.

The installer should ensure that suitable ductwork, electrical isolation and airflow commissioning are provided.

For panel, ceiling or interior wall installations, the manufacturer's installation instructions specify a 130mm mounting hole for the 125mm fan.

Bathroom zone suitability must be assessed as part of the complete electrical installation.