Clayton Certainty Fog Signal

The Clayton Certainty Railway fog signal is a small metal device containing a limited quantity of explosive. 

In use, the device is placed on the running surface of a rail such that any rail-mounted vehicle passing over it would cause it to explode, and in so doing, alert the driver of the vehicle to a hazard on the line ahead. A common use for railway fog signals is to protect possessions.

Within the rail industry fog signals are also known as signal detonators, this can cause confusion for those outside the industry as what is normally known as a detonator is actually an initiator for a larger charge.

The Clayton Certainty Railway Fog Signal has been manufactured by the Clayton Penistone Group since 1895 with the basic design dating back to 1860. The design has remained unchanged during this time as it offers high standards of safety with total reliability.The Certainty Railway Fog Signal which is approved for use within the UK Rail Industry is primarily the lead clip version. Which is hand placed on the rail, a small number of automatic placers still exist in service and use different mounting method.

Whilst the fundamental design has remained unchanged, we constantly monitor the quality to ensure it is never compromised and physically test a sample unit from each production batch every six months for the whole of its shelf life (5 Years from manufacture)

The Clayton Certainty Fog Signal gained CE Certification in 2018, and became UKCA Certified in 2022. As part of this process the product was submitted & tested by an approved body for Pyrotechnics to both UK & EU legal requirements which is audited on an annual basis to ensure that the device remains compliant with the relevant legislation.

In line with the requirements of both the CE & UKCA certification the device must only be used in accordance with the specification and the Product Safety Data Sheet, a copy of which is provided within each shipping box.

We maintain certification licences for approved Dangerous Goods packaging which is a legal requirement for all transportation other than by the end use.

This includes fully authenticated destruction testing by an approved agency to ensure that the unit is safe to handle and transport.

We are able to ship to distributors and large users worldwide using approved Dangerous Goods transport.


Clayton Certainty Product Safety Data Sheet Dated 15th March 2024


Detonator Uses

The use of Clayton Certainty Railway fog signals on railway lines are defined within the handbook for the relevant rail network. In the United Kingdom these can be obtained from the RSSB.

Fog Signals are typically used to provide an audible warning to both rolling stock operators and trackside workers of a dangerous condition created by approaching rolling stock.

examples of there current use are :-

Protecting unsafe lines - three detonators at 20m intervals  2km from point of danger,

Temporary block working - one detonator at the danger signal, one detonator at exit signal.

Possession Protection & Line Blockage Possession , three detonators at 20m intervals at entrance and exit to possession.

 Always consult the handbook and Safe System of work for your Railway Network prior to using Detonators.



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Clayton Penistone Group, Westhorpe Works, Halifax Road, Penistone, Sheffield
South Yorkshire England S36 7EY

T: +44 (0) 1226 763130
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