TAS-33 Thatch Alert

The Thatch Alert Chimney Monitor System has been specifically designed to monitor the temperature of the chimney brickwork at the point where it meets the thatch.

Product Description

The system acts as an early warning device to inform the home owner of potential high temperatures.

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The Facts

Wood burners and multi-fuel stoves can generate very high gas temperatures; this in turn can be transferred through the brickwork of the chimney to the thatch, this is known as Heat Transfer. Heat Transfer is further increased at the point that the thatch meets the chimney; this is due to the insulating properties of the thatching material.

The Heat Transfer process can cause thatch to smoulder and ignite if temperatures in excess of 200ºC are reached.

Studies show that wood burners and multi-fuel stoves being installed into thatched properties are a major cause of thatch fires.

TAS Faulty ChimneyThis is mainly due to faulty chimneys, poorly or incorrectly fitted liners, combined with high flue gas temperatures being generated by these efficient stoves.

Worse still the thatch is at a much greater risk of the effects of Heat Transfer if the chimney is not lined, additionally the transfer process can be accelerated if the condition of the brick work or mortar has degraded over the years.

In many cases the lower section of the chimney has not seen the light of day for over 20 years due to the thatch being in place.

A modern insulated liner system that has been correctly installed and maintained to current building regulations will dramatically reduce the risk of Heat Transfer occurring in the first place.

Note: Properties with normal open fires can also suffer from the effects of Heat Transfer

Other Chimney Related Issues

Many chimneys are not lined correctly, for example, if a flexi liner is installed incorrectly and is therefore allowed to touch the side of the chimney it can cause a hot spot, which in turn will dramatically accelerate the process of heat transfer.

Bricks missing, again as already mentioned it impossible to check the condition of the chimney at the point that it passes through the thatch, useless the thatch is removed or an internal CCTV type survey is completed.

Heat Transfer Diagram

The Heat Transfer process can cause thatch to smoulder and ignite if temperatures in excess of 200°C are reached.

This Heat Transfer Diagram represents the temperature within the thatch resulting from an average flue gas temperature of 300°C and a thatch depth of 1m.

Thatch Heat Transfer Diagram

.. 250°C
.. 200°C
.. 150°C
.. 100°C
.. 50°C
.. Ambient temperature of thatch
Supplied by: The National Society of Master Thatchers

With over 60,000 thatched properties in the UK and an ever increasing number of wood burners and multi-fuel stoves being installed, it is not surprising that thatch fires occur.

TAS-33 Thatch Alert System

Thatch Alert Chimney Monitor System has been specifically designed for this application and therefore consists of bespoke functions to allow the system to be tailored to each property.

The Thatch Alert Chimney Heat Monitor System works very differently to other early warning devices, as it continues to monitor the temperature after the alarm has been triggered and therefore allows the homeowner to carry on monitoring the temperature once they have taken preventative measures.

Once installed, in the event of high temperatures being recorded, the system will trigger an audible alarm, allowing the owner to take action.


  • Adjustable temperature setting – This allows our engineers to change the alarm activation temperature point, due to the varying types of chimney construction, size and liners fitted.
  • Other audible alerts – Thatch Alert also has built in functions to warn the homeowner of: low battery, transmission issues and detached probes.
  • Battery powered – Using smart energy saving technology, we have been able to power the Thatch Alert system using standard AA Alkaline batteries. This removes the need for homeowner to provide additional mains power supplies in the loft space. The batteries will last for a minimum of 12-months, with the homeowner getting a 2-month warning to replace the batteries.
  • Large display – The Thatch Alert receiver is fitted with a large and easy to read display that constantly shows the temperature of the chimney brickwork at the point that it meets the thatch.


The Thatch Alert Chimney Heat Monitor is available exclusively through Thatching Advisory Services and installed by our team of experienced engineers.

The system is made up of two thermocouple probes, a transmitter and a receiver. The two probes, which are plugged into the transmitter, are securely attached to the chimney stack. The transmitter will then send a signal to the receiver which will display the temperature of both probes.

For the system to work correctly the probes need to be located half way down the thickness of the thatch. This is to ensure that the Thatch Alert Chimney Monitor System is monitoring the point that heat transfer is most likely to occur.

On completion of each installation the homeowner is issued with the following:

  • Comprehensive Operating Manual
  • Quick Reference Guide
  • Certificate of Installation – This can then be forwarded to the home owner`s insurance company

Ongoing Support

Each Thatch Alert Chimney Monitor System comes with a full 12-month guarantee covering both the product and the installation. In addition to this we offer a telephone support service during normal office hours.

Each homeowner is also offered a Comprehensive Support Contract which commences on the 1st anniversary of the installation. This contract includes an annual site visit to inspect/test the system and replace the batteries. Providing the system has passed the inspection a new 12-month certificate will be issued.


As with all homeowners that contact us, we first ask if they have a liner fitted and if so what type. If the answer is no or they are not sure, we direct them to the find the installer section on the HETAS website.

The Thatch Alert system is not a replacement or compromise for a poorly performing or faulty flue/chimney. The system is totally optional for any homeowner that is looking for extra peace of mind over and above a correctly lined chimney.

For more information on this and other Thatch Fire Protection Products and Systems, please contact us on 08455 20 40 60 or use our enquiry form.

‘Leading the way in Thatch Fire Prevention’