High-voltage electrical installations can present serious risks to employees, contractors and members of the public.

From substations and electrical compounds to industrial switchgear and overhead power lines, it is important that people can recognise electrical hazards before entering or approaching a dangerous area.

High Voltage Warning Signs help communicate these risks using prominent wording and recognisable electrical warning symbols.

But where should these signs be displayed? Does every electrical cupboard need a High Voltage notice? And how do you choose the correct size and material?

This practical UK guide explains the main locations where High Voltage Signs may be appropriate, how to position them effectively and what businesses should consider when reviewing their electrical safety signage.

What Is a High Voltage Warning Sign?

A High Voltage Warning Sign communicates the presence of an electrical installation or hazard involving high voltage.

These signs commonly feature a black lightning bolt inside a yellow warning triangle, accompanied by wording such as:

Danger High Voltage
Warning High Voltage
Danger of Death
High Voltage Keep Out

The appropriate wording depends on the installation, its identified hazards and any relevant access restrictions.

A general Danger Electricity Sign may be more suitable where an electrical hazard exists but a High Voltage warning would be inaccurate.

Why Are High Voltage Signs Important?

Electrical hazards aren't always obvious to somebody unfamiliar with an installation.

Equipment may be housed behind an enclosure, located within a plant room or positioned inside a restricted compound.

Appropriate warning signs can help:

Identify high-voltage hazards.
Alert people before they enter a hazardous area.
Reinforce restricted access arrangements.
Communicate important safety information to contractors.
Support workplace electrical safety procedures.
Distinguish hazardous electrical installations from general equipment.

However, a warning sign doesn't make electrical equipment safe.

It must support suitable electrical protection, access controls, maintenance, isolation procedures and other necessary risk-management measures.

Where Should High Voltage Warning Signs Be Displayed?

The most appropriate position depends on the electrical installation and how people approach it.

The following locations are particularly relevant when reviewing high-voltage signage.

1. Electrical Substations

Electrical substations are among the most recognisable locations for High Voltage Warning Signs.

Depending on the installation, suitable notices may include:

Danger High Voltage.
Danger of Death.
Keep Out.
No Unauthorised Access.

Warning signs should be positioned where people can recognise the danger before entering or approaching the restricted area.

Consider the main entrance, gates, doors and other relevant access points.

Substation owners and operators should follow the specific technical, safety and signage requirements applicable to their installations.

2. High-Voltage Switchgear Rooms

Switchgear rooms may contain electrical equipment that requires controlled access and specialist working procedures.

Appropriate signage can help identify the hazard and reinforce access restrictions.

Potential positions include:

Main room entrances.
Restricted access doors.
Relevant equipment enclosures.
Other locations identified through the risk assessment.

A High Voltage notice should accurately reflect the equipment inside the room.

Where multiple electrical hazards exist, consider whether additional equipment-specific information is necessary.

3. Electrical Compounds

Outdoor electrical compounds may contain transformers, switchgear and other electrical infrastructure.

These areas can be exposed to weather and may have multiple access points.

Consider positioning High Voltage Signs on:

Entrance gates.
Relevant perimeter fencing.
Access doors.
Equipment enclosures, where appropriate.

The number and position of notices should reflect the compound's layout, visibility and identified risks.

Avoid assuming that one warning at the main entrance will always be sufficient for a larger installation.

4. Transformer Installations

Transformers and associated electrical equipment may require suitable hazard identification.

Where high voltage is present, an appropriate warning sign can help communicate the risk.

Potential locations include transformer enclosure doors, restricted equipment areas and relevant access points.

Choose wording that accurately reflects the installation.

For example, a transformer installation shouldn't automatically be labelled with an arbitrary voltage simply because that value appears on an available sign.

5. Industrial Factories & Manufacturing Sites

Large industrial facilities may contain high-voltage electrical distribution systems, dedicated plant rooms and restricted electrical equipment.

Suitable High Voltage Signs can help communicate hazards to:

Maintenance personnel.
Contractors.
Facilities teams.
Employees working nearby.
Authorised visitors.

Consider the normal routes people use through the premises and whether they can recognise the hazard before approaching the relevant installation.

6. Construction Sites

Construction sites may contain electrical installations and infrastructure that present high-voltage hazards.

These can include existing site substations, electrical compounds and overhead power lines.

Suitable warning notices may be appropriate at relevant access points and locations identified through the site risk assessment.

However, construction sites shouldn't rely on signage alone.

Work involving or taking place near electrical infrastructure requires suitable planning, competent advice and appropriate precautions.

7. Overhead High-Voltage Power Lines

Overhead power lines can create serious risks where vehicles, lifting equipment, scaffolding or agricultural machinery operate nearby.

Warning signs may be relevant around:

Construction access routes.
Farm tracks.
Industrial yards.
Areas used by cranes or lifting equipment.
Relevant vehicle entrances.

The message should be visible before drivers or operators approach the hazardous location.

A generic High Voltage Sign may not communicate the full nature of an overhead-line hazard. A more specific Overhead Electric Cables warning may be appropriate.

Warning signs must support suitable exclusion arrangements, safe working distances and other necessary controls.

8. Restricted Electrical Maintenance Areas

Some electrical maintenance activities require temporary access restrictions or additional warnings.

Depending on the circumstances, relevant notices may include:

Danger High Voltage.
No Unauthorised Access.
Do Not Switch On.
Men Working on Equipment.
Other site-specific electrical instructions.

Temporary notices must accurately reflect the current working arrangements.

A warning sign or maintenance tag should never be treated as proof that equipment has been safely isolated.

9. Commercial Buildings & Plant Rooms

Some larger commercial buildings, hospitals, educational facilities and industrial premises contain high-voltage infrastructure.

Where relevant, appropriate warning signs may be displayed at:

Dedicated electrical plant rooms.
High-voltage switch rooms.
Restricted distribution areas.
Associated equipment enclosures.

However, not every ordinary electrical cupboard or distribution board contains high-voltage equipment.

Always verify the installation before choosing the sign.

Does Every Electrical Cupboard Need a High Voltage Sign?

No.

An electrical cupboard may contain equipment that requires a general electrical hazard warning without necessarily containing high-voltage equipment.

The terms Danger Electricity and Danger High Voltage shouldn't be treated as interchangeable.

A Danger Electricity Sign communicates a general electrical hazard.

A High Voltage Sign communicates a more specific condition.

If you're unsure which warning accurately describes an installation, consult a competent electrical professional rather than selecting a sign based on appearance alone.

High Voltage Signs vs Danger of Death Signs

Both signs can communicate serious electrical hazards, but their wording is different.

Sign	Main message
Danger Electricity	General electrical hazard
Danger High Voltage	High-voltage electrical hazard
Danger of Death	Potentially fatal hazard
No Unauthorised Access	Entry restriction
Overhead Electric Cables	Specific overhead electrical hazard

Some installations may require a combination of warnings and access restrictions.

Choose the messages according to the actual risks and avoid displaying unnecessary or conflicting notices.

Where Exactly Should High Voltage Signs Be Positioned?

Even the correct sign may be ineffective if it is poorly positioned.

Consider the following factors.

At the Point of Access

For a general hazard affecting an entire room or enclosure, an entrance door or gate is often an appropriate location.

The warning should be visible before somebody enters the area.

Near the Relevant Hazard

Where the hazard relates to a particular item of equipment, consider positioning the sign in its immediate vicinity, subject to the installation's requirements.

At a Suitable Viewing Height

Choose a mounting height that allows the intended audience to recognise the warning easily.

Consider people approaching on foot as well as drivers or machinery operators where relevant.

Clear of Obstructions

Avoid positioning signs:

Behind stored equipment.
Where an open gate hides the message.
Behind vegetation.
Where parked vehicles block the view.
In poorly illuminated positions.
Beyond the point where somebody encounters the hazard.

At Multiple Access Points Where Necessary

A large electrical compound or industrial installation may have several entrances.

Review all relevant approach routes rather than relying solely on the main entrance.

How Many High Voltage Warning Signs Do I Need?

There isn't one universal number of signs suitable for every high-voltage installation.

The appropriate quantity depends on factors including:

The extent of the hazard.
The size of the area.
The number of entrances.
The position of electrical equipment.
Viewing distance.
Access arrangements.
Existing warning systems.
Site-specific requirements.

A single-door switchgear room will have different signage considerations from a large outdoor electrical compound with several access points.

The objective is to ensure that relevant people receive a clear warning before encountering the hazard.

What Size High Voltage Sign Should I Choose?

Sign size should reflect the viewing distance and intended mounting position.

A warning attached to an equipment enclosure may be viewed at close range.

A sign positioned on a perimeter fence or intended for people approaching from a distance may need to be more prominent.

Consider:

Viewing distance.
Symbol size.
Text size.
Lighting conditions.
Mounting height.
Approach direction.
Colour contrast.
Surrounding obstructions.

The warning should be easy to recognise and understand.

What Colour Should a High Voltage Warning Sign Be?

Recognised electrical warning signs commonly use a black lightning bolt inside a yellow triangle with a black border.

This follows the established visual design for warning signs.

The yellow triangle identifies a potential hazard, while accompanying wording can provide additional information about the nature of the electrical risk.

A prohibition notice, such as No Unauthorised Access, communicates a different message and uses a different recognised sign design.

Where applicable, use appropriate standardised symbols rather than relying solely on written instructions.

Are High Voltage Signs a Legal Requirement in the UK?

Electrical safety responsibilities arise under legislation including the Electricity at Work Regulations 1989.

The Health and Safety (Safety Signs and Signals) Regulations 1996 also require suitable workplace safety signage where significant risks remain after other relevant safety measures have been implemented and signs can help reduce those risks.

The correct signage depends on the installation, its hazards and the responsibilities of the relevant dutyholder.

There isn't one universal High Voltage Sign that must be displayed on every electrical cupboard or item of equipment.

Some installations, particularly those forming part of electricity distribution infrastructure, may also be subject to additional specific requirements.

Appropriate warning signage should support wider electrical safety arrangements, not replace them.

Can High Voltage Signs Replace Physical Barriers?

No.

A warning sign communicates a hazard but doesn't prevent somebody from entering a restricted area or coming into contact with electrical equipment.

Where the installation requires suitable enclosures, barriers, restricted access, electrical protection or other controls, these measures remain necessary.

Similarly, maintenance warning notices must not replace proper electrical isolation procedures.

Choosing Materials for High Voltage Signs

High Voltage Signs may be installed indoors or outdoors.

Choose a material suitable for the mounting surface, environment and intended lifespan.

Depending on the product, options may include:

Self-Adhesive Vinyl: Suitable for appropriate smooth, clean surfaces.

Rigid Plastic: A practical option for many general workplace applications.

Recycled Plastic: Available across selected signage products.

Aluminium Composite: A durable option for suitable longer-term installations, including exposed outdoor locations.

Where signs are used outdoors, consider weather exposure, secure fixing and routine inspection.

For specialised electrical equipment, follow any applicable installation and operator specifications.

Common High Voltage Signage Mistakes

Avoid these frequent problems:

Using High Voltage wording where it doesn't accurately describe the installation.
Missing warnings at relevant access points.
Positioning signs where they are obscured by open doors or gates.
Displaying incorrect voltage information.
Using a sign that is too small for the viewing distance.
Failing to replace faded or damaged notices.
Overlooking secondary entrances.
Using generic wording where a specific hazard warning is needed.
Leaving outdated temporary maintenance notices in place.
Assuming that displaying a warning sign removes the need for other safety controls.

Regularly review your signage when electrical installations or site access arrangements change.

High Voltage Warning Sign Placement Checklist

Use this practical checklist when reviewing your premises or ordering replacement signs.

Identifying the Hazard

Is high voltage actually present?
Has the installation been assessed by an appropriate competent person?
Is the selected warning accurate?
Are additional electrical hazards present?
Are access restrictions necessary?

Choosing the Signs

Danger High Voltage.
Danger of Death, where appropriate.
Danger Electricity, where appropriate.
No Unauthorised Access, where required.
Overhead Electric Cables, where relevant.
Correct voltage-specific information, where needed.

Positioning

Main entrances have been reviewed.
Secondary access points have been considered.
Warnings are visible before the relevant hazard.
Signs are mounted at a suitable height.
Viewing distance has been considered.
Signs aren't obscured by doors, equipment or vegetation.
Outdoor warnings are clearly visible.

Materials & Maintenance

The material is suitable for the environment.
Fixings are secure.
Signs remain legible.
Damaged notices are replaced.
Temporary notices are reviewed when work finishes.
Signage is updated when installations change.

Important: This is a signage selection checklist, not a substitute for a suitable electrical risk assessment or the specific technical requirements applicable to an installation.

A Final Check Before Ordering High Voltage Signs

Before ordering, walk through the site and identify every relevant route towards the electrical installation.

Start at the main entrance and consider how employees, contractors, maintenance personnel and other authorised users approach the area.

Ask yourself:

Can people recognise the high-voltage hazard before entering?
Are access restrictions clearly communicated?
Is the wording technically accurate?
Are warning signs visible from all relevant approaches?
Is the sign material suitable for its location?
Are existing notices damaged, faded or outdated?

A simple review can help identify gaps in electrical hazard communication.

Shop High Voltage Warning Signs at Safety Sheep

Safety Sheep supplies High Voltage Warning Signs and Electrical Safety Signs for UK businesses, factories, construction sites, warehouses and commercial premises.

Our range includes Danger High Voltage, Danger Electricity, Danger of Death, Overhead Electric Cables and voltage-specific warning notices.

Choose from a selection of sizes and durable materials suitable for indoor and outdoor use.

Made in Britain, with bulk savings available for businesses and trade customers.

Explore our full range of Electrical Safety Signs to find suitable warnings for your workplace.

Think Safety. Think Sheep.

High Voltage Warning Signs: Where Should They Be Displayed?