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CAT & Genny calibration keeps your detection equipment accurate, compliant, and ready to prevent costly underground strikes.

Used every day across construction, utilities, and civil engineering, the Cable Avoidance Tool (CAT) and Signal Generator (Genny) are vital for locating buried services before excavation.

But without proper calibration, even a working unit can give false confidence – and false readings.

This guide explains how CAT & Genny systems work, why regular calibration is required under PUWER and HSG47, and what’s involved to stay compliant and protect your workforce.

🧭 Jump to:

What is a CAT & Genny?

The Cable Avoidance Tool (CAT) and Signal Generator (Genny) are used to detect buried infrastructure like:

• Electrical cables
• Water and gas mains
• Fibre-optic and telecom lines

The CAT can search for naturally occurring or deliberately applied electromagnetic signals using several detection modes. Operators should normally use more than one mode because each mode identifies different types of signal and has different limitations.

The main Power, Radio and Genny modes are explained in more detail below.

How Does a CAT & Genny Work?

A CAT detects electromagnetic signals associated with underground cables and metallic services. Some signals are produced naturally by live electrical cables or re-radiated radio signals, while others are deliberately applied using the Genny.

The Genny can apply a signal to a service in several ways:

• Direct connection: The Genny is physically connected to an accessible metallic service, allowing the signal to travel along it.
• Signal clamp: A clamp is placed around an accessible cable or pipe to apply the signal without making a direct electrical connection.
• Induction: The Genny is placed above the suspected route and broadcasts a signal into nearby conductive services.
• Sonde or traceable rod: A small transmitter or traceable accessory is introduced into a duct, drain or pipe so its route can be followed.

The CAT is then used to detect and trace the applied or naturally occurring signal from the surface.

What Are the CAT & Genny Modes?

CAT scanners use different modes to search for different types of electromagnetic signal. The exact names and features vary between manufacturers, but most units include Power, Radio and Genny modes.

A reliable survey should not normally depend on one mode alone. Operators should sweep the area systematically using the available passive modes before applying the Genny signal to trace particular services more accurately.

How to Use a CAT & Genny

CAT & Genny equipment should be used by someone who has received suitable instruction and understands both the equipment and its limitations.

A typical scanning process includes:

1. Review service information: Check current utility plans, previous survey information and visible site features before starting the scan.
2. Complete pre-use checks: Inspect the CAT, Genny, leads and accessories for damage. Confirm the batteries are charged, the self-test completes correctly and the calibration or inspection status is current.
3. Survey the area visually: Look for inspection covers, meter boxes, service entries, street furniture, patched surfaces and other signs of underground services.
4. Scan in Power Mode: Sweep the full work area systematically to search for signals from loaded electrical cables.
5. Repeat in Radio Mode: Rescan the same area to identify metallic services carrying re-radiated radio signals.
6. Apply the Genny signal: Use direct connection, a clamp, induction or a suitable accessory to apply a signal to the service being traced.
7. Trace the complete route: Follow the detected signal beyond the immediate excavation area rather than marking only a single point.
8. Cross-check the reading: Scan from different directions and at right angles to the suspected service route.
9. Mark the findings: Clearly mark the likely position and route of each detected service using an agreed site system.
10. Confirm through safe excavation: Use appropriate safe digging techniques and trial holes where required. Detection equipment should support, not replace, safe excavation controls.

HSG47 provides further guidance on planning, locating services and carrying out excavation safely.

Can a CAT & Genny Detect Water Pipes?

A CAT and Genny can detect some underground water pipes, but detectability depends on the pipe material and whether a traceable signal can be applied.

• Metallic water pipes: These can often be detected if they carry a suitable passive signal or if the Genny signal can be applied directly or using a clamp.
• Plastic pipes with tracer wire: The tracer wire may be energised using the Genny and followed using the CAT.
• Plastic pipes without tracer wire: These cannot normally be detected directly because plastic does not conduct an electromagnetic signal.
• Accessible plastic pipes, ducts or drains: A sonde, Flexitrace or traceable rod may be inserted so the route can be followed from the surface.

The absence of a reading does not prove that no water pipe is present. Older plans, missing tracer wires, inaccessible entry points and non-conductive materials can all limit detection.

What mode should you use to find a water pipe?

For a metallic water pipe, Genny Mode will often provide the clearest result where a signal can be applied directly or through a clamp. Power Mode is generally associated with live electrical cables, while Radio Mode may detect some metallic pipes if they are carrying re-radiated radio signals.

Plastic water pipes require a tracer wire, sonde, Flexitrace or another traceable accessory. Changing the CAT mode alone will not make an untraceable plastic pipe detectable.

Why Calibration Matters

Daily use, impacts, vibration, water ingress, damaged antennas, ageing components and battery issues can all affect the sensitivity or reliability of a CAT & Genny.

A unit may power on and complete its basic self-test while still producing readings that fall outside the expected tolerances.

If the equipment has not been checked and calibrated appropriately:

• Underground services may be missed or incorrectly traced.
• False or unstable readings may cause unnecessary excavation delays.
• The employer may be unable to demonstrate that the equipment was properly maintained.
• An equipment fault may contribute to a cable or service strike.

HSG47 says locating devices should be kept in good working order and checked and calibrated regularly. PUWER also requires work equipment to be maintained in an efficient state, in efficient working order and in good repair.

Calibration provides traceable evidence that the equipment has been tested against controlled reference signals and was operating within the required tolerances at the time of the test.

How Often Should a CAT & Genny Be Calibrated?

Many CAT & Genny units are placed on a 12-month calibration cycle, but the correct interval should be based on the manufacturer’s instructions, the frequency of use, the working environment and the condition of the equipment.

Calibration or further testing may be required sooner where the equipment has:

• Been dropped or suffered a significant impact.
• Been exposed to water, excessive moisture or contamination.
• Started producing inconsistent, weak or unexpected readings.
• Failed a self-test or pre-use check.
• Been repaired or had components replaced.
• Been used intensively in harsh site conditions.

For high-use equipment, employers may also introduce interim functional checks between formal calibration dates.

What’s Involved in Calibration?

A full CAT & Genny calibration typically includes:

• Visual inspection: The housing, controls, display, antenna, battery compartment, leads and accessories are checked for damage or contamination.
• Functional testing: The controls, speaker, display, sensitivity adjustment and self-test functions are checked.
• Power Mode testing: The CAT is tested against controlled signals representing detectable electrical services.
• Radio Mode testing: The unit’s response to appropriate radio-frequency reference signals is checked.
• Genny Mode testing: The CAT and signal generator are tested across the relevant frequencies and operating methods.
• Accuracy and sensitivity checks: Results are compared with traceable reference equipment and the manufacturer’s permitted tolerances.
• Adjustment or realignment: Where the model allows, readings outside tolerance are adjusted before the equipment is tested again.
• Final pass or fail decision: Equipment is only returned to service once it has completed the required checks successfully.
• Calibration record: A certificate is issued identifying the equipment, serial number, calibration date, results and next recommended due date.

Depending on the model and its condition, calibration may also identify the need for repairs, replacement leads, battery contacts, housings, firmware updates or other corrective work.

At Velocity Safety, CAT & Genny calibration can be completed on-site or through the workshop service, with traceable certification supplied for each unit.

Do CAT Scanners Need Calibration?

Yes. CAT scanners should be checked and calibrated at appropriate intervals to confirm that their detection modes, sensitivity and operating functions remain within the required tolerances.

A basic self-test or successful power-on check does not provide the same assurance as calibration against controlled reference signals.

Equipment that has not been properly maintained or calibrated may:

• Miss services that should have produced a detectable signal.
• Produce weak, unstable or misleading readings.
• Fail to apply or detect the correct Genny frequencies.
• Leave the employer without adequate maintenance and calibration records.

An overdue calibration date does not automatically prove that a unit is inaccurate, but it does mean there may be insufficient current evidence that the equipment remains reliable. The unit should be assessed before it is relied upon for excavation work.

What the HSE and Manufacturers Say

HSG47 explains that service-locating equipment should be maintained in good working order and regularly checked and calibrated. It also emphasises that operators must understand how to use the equipment and recognise its limitations.

Manufacturers publish model-specific instructions covering:

• Pre-use and self-test procedures.
• Recommended calibration or service intervals.
• Checks required after impact, water exposure or suspected faults.
• Permitted operating tolerances.
• Compatible transmitters, clamps, sondes and accessories.

The manufacturer’s instructions should therefore be used alongside the employer’s PUWER maintenance programme and the safe-working principles set out in HSG47.

Neglecting checks, calibration or known defects may become significant if inaccurate equipment contributes to a service strike, injury or project disruption.

On-Site vs Off-Site Calibration Options

Velocity Safety provides flexible options:

Additional services:

• Equipment sales and refurbs
• Repairs and servicing
• Operator training and technical support

FAQs

Here are the most common questions about CAT and Genny use, calibration, certificates, detection limits and HSG47 compliance.

What is a CAT & Genny?

A CAT and Genny is a cable avoidance system used to help locate underground services before excavation. The CAT detects electromagnetic signals, while the Genny applies a traceable signal to cables, metallic pipes or suitable tracing accessories.

What does CAT and Genny stand for?

CAT stands for Cable Avoidance Tool. Genny is the commonly used shortened name for the Signal Generator used alongside the CAT.

How does a CAT & Genny work?

The CAT detects electromagnetic signals associated with buried cables and metallic services. The Genny applies a controlled signal through direct connection, a clamp or induction, allowing the CAT operator to trace a particular service more accurately.

What are the CAT & Genny modes?

Power Mode searches for signals produced by loaded electrical cables. Radio Mode detects re-radiated radio signals carried by some metallic services. Genny Mode detects a signal deliberately applied using the signal generator. Some models also include manufacturer-specific AllScan, Avoidance or Auto modes.

How do you use a CAT & Genny safely?

Review available service plans, inspect the equipment, scan the full area systematically in the available passive modes, apply the Genny signal where appropriate, trace each detected service from more than one direction and clearly mark the results. The findings should then be combined with safe excavation techniques rather than treated as proof that the ground is clear.

Can you use a CAT without a Genny?

A CAT can be used in passive Power and Radio modes without a Genny. However, passive signals are not always present or detectable. Using the Genny allows a specific signal to be applied and usually provides a more reliable way to trace suitable services.

Can a CAT & Genny detect water pipes?

It can detect metallic water pipes where a suitable signal is present or can be applied. Plastic pipes generally cannot be detected directly unless they include a tracer wire or can be traced using a sonde, Flexitrace or another suitable accessory.

What mode should you use to find a water pipe?

Genny Mode is generally the most useful option for tracing a metallic water pipe where the signal can be applied directly or using a clamp. Radio Mode may detect some metallic pipes carrying re-radiated signals. Plastic pipes require a tracer wire or traceable accessory rather than a different CAT mode.

Can a CAT & Genny detect every underground service?

No. Detection depends on the service material, signal strength, depth, surrounding ground conditions, nearby services and the equipment used. Non-conductive pipes, unenergised cables and poorly positioned services may not produce a detectable signal.

Does a CAT & Genny replace utility plans?

No. Service plans and CAT & Genny scanning should be used together. Plans can be incomplete or inaccurate, while detection equipment also has limitations. Neither should be relied upon as the sole control before excavation.

Does a CAT & Genny show the exact depth of a service?

Some compatible CAT and Genny systems can estimate depth when the correct active signal and operating method are used. The result is an estimate rather than a guarantee and can be affected by signal distortion, neighbouring services and incorrect technique.

How often should a CAT & Genny be calibrated?

Many units are placed on a 12-month calibration cycle, but the correct interval depends on the manufacturer’s instructions, equipment condition, frequency of use and working environment. The unit should also be checked after impact, water ingress, repair or unreliable readings.

Is CAT & Genny calibration legally required?

UK legislation does not set one universal calibration interval for every CAT & Genny. However, PUWER requires work equipment to be properly maintained, and HSG47 says locating equipment should be regularly checked and calibrated. Employers should follow the manufacturer’s instructions and maintain appropriate records.

What does CAT & Genny calibration test?

Calibration checks the relevant detection modes, frequencies, sensitivity, controls, display, speaker and transmitter functions against controlled reference signals. Where permitted, equipment outside tolerance is adjusted and retested before it is passed.

What happens if a CAT & Genny fails calibration?

The equipment should not be returned to normal use until the fault has been investigated. Depending on the issue, it may require adjustment, repair, replacement components or replacement of the unit.

How long does a CAT & Genny calibration certificate last?

A calibration certificate records the equipment’s condition and test results on the date of calibration. Many providers also state a recommended next due date, commonly 12 months later. The unit should still be assessed sooner if it is damaged, exposed to water or begins producing unreliable readings.

What should a CAT & Genny calibration certificate include?

The certificate should normally identify the equipment make, model and serial number, the calibration date, the tests completed, the results, any adjustments made, the organisation or engineer completing the work and the recommended next calibration date.

Can you calibrate a CAT & Genny on-site?

Yes. Velocity Safety offers on-site CAT & Genny calibration for businesses that need to reduce equipment downtime, as well as workshop calibration for units requiring further diagnostics, servicing or repair.

Resources & Further Guidance

• PUWER 1998: Work Equipment Regulations
• HSE HSG47: Avoiding Danger from Underground Services (PDF)

Stay compliant, stay protected – even when your site moves.

Whether you’re managing a construction site, outdoor event, or temporary facility, fire safety isn’t optional – but wall-mounting extinguishers often isn’t practical.

That’s where fire extinguisher trolleys (also called mobile fire points) offer a compliant, mobile solution.

In this guide, we’ll explain:

• What Is a Fire Extinguisher Trolley?
• Where Are Fire Trolleys Used?
• What Should a Fire Point Include?
• Are Fire Trolleys a Legal Requirement?
• Do I Need a Mobile Fire Point?
• Fire Trolley vs Wall Mount: Which Is Best?
• Buying or Hiring Fire Trolleys
• Fully Serviced Fire Points
• FAQs
• Resources

What Is a Fire Extinguisher Trolley?

A fire extinguisher trolley is a wheeled metal frame that holds one or more extinguishers and accessories. It allows fire equipment to remain:

• Mobile
• Visible
• Secure
• Accessible on dynamic or temporary sites

Also known as mobile fire points, trolleys are widely used when fixed wall mounting is not viable.

Where Are Fire Trolleys Used?

Fire trolleys are standard in environments where layout changes frequently or permanent infrastructure is limited, such as:

• Construction & demolition sites
• Temporary modular buildings or site cabins
• Outdoor events, markets, or exhibitions
• Fuel yards and forecourts
• Warehouses and loading bays
• Film sets or mobile production sites

💡 Example: On a live construction site, cabins may move every few weeks. A fire point on wheels ensures extinguishers stay where people need them – even when the layout changes.

What Should a Fire Point Include?

A fire point is more than just a frame. It should be a complete station, designed to meet the requirements of BS 5306-8, HSE construction guidance, and the Fire Safety Order 2005.

Minimum recommended components:

• ✅ Fire extinguishers (typically CO₂ ,Foam, Dry Powder, Wet Chemical or Water)
• ✅ Fire safety signage (e.g. extinguisher ID, fire action notice)
• ✅ Protective housing (to shield from weather/tampering)
• ✅ Accessibility & visibility from common working areas

Additional miscellaneous equipment:

• 🔲 Fire blanket
• 🔲 Fire bucket
• 🔲 Manual call point or alarm bell
• 🔲 First aid kit or defibrillator mount
• 🔲 Site plan or contractor-specific signage

BS 5306-8 sets out UK guidance for fire extinguisher selection and positioning. BS 5306-3 covers servicing and maintenance.

Are Fire Trolleys a Legal Requirement?

No UK law specifically requires the use of fire trolleys – but fire points are required, and trolleys are the only way to deliver them on sites where wall mounting is not feasible.

Under the:

• Regulatory Reform (Fire Safety) Order 2005
• Construction (Design and Management) Regulations 2015 (CDM 2015)

You are legally responsible for:

• Providing suitable fire-fighting equipment
• Ensuring it is readily accessible and visible
• Preventing damage, misuse, or obstruction

If those duties can’t be met using wall-mounted systems, a mobile fire point is the compliant solution.

Do I Need a Fire Point on My Site?

Ask yourself:

• Is your site temporary or under phased development?
• Are you operating outdoors or across split zones?
• Are wall mounts impossible due to layout or surfaces?
• Do facilities like site cabins move during the project?

If the answer to any of these is yes – a fire trolley is the most effective way to remain compliant with your fire safety obligations.

Fire Trolley vs Wall Mount: What’s Best?

While both options serve the same core function – making fire extinguishers accessible – each has pros and cons depending on your site layout, mobility needs, and risk factors. Here’s how they compare at a glance:

Verdict: Use wall mounts for static indoor environments. Use fire trolleys when mobility, visibility, or layout makes wall mounting impractical.

Buy or Hire a Fire Extinguisher Trolley

Velocity Safety offers flexible options for all site types:

• Buy assembled or flat-packed units
• Short-term hire for events or temporary jobs
• Fully stocked trolleys with BS-certified extinguishers
• Fire extinguisher servicing and maintenance packages
• Custom signage and contractor branding if needed
• Fire Extinguisher Commissioning & Decommissioning Services

We’ll advise on the right extinguisher types and trolley setup based on your site and risk profile.

FAQs

What is a fire extinguisher trolley?

A mobile fire point – typically a wheeled metal stand holding multiple extinguishers, signage, and safety accessories.

Is a fire trolley a legal requirement?

Not by name – but if fixed installations aren’t possible, a fire trolley is one way to meet the requirements.

Do I need one on my site?

If your site is temporary, evolving, or lacks permanent walls, yes – a fire trolley is a practical compliance solution.

What extinguishers are used?

This would vary dependent on the risk. Get in touch and we’ll be happy to advise.

Do they need servicing?

Yes – extinguishers must be serviced annually in accordance with BS 5306-3.

See also: Fire Extinguisher Servicing & Maintenance

Resources & Further Guidance

• Regulatory Reform (Fire Safety) Order 2005
• BS 5306-8:2023 – Fire Extinguisher Positioning (Summary)
• BS 5306-3:2017 – Fire Extinguisher Servicing Requirements
• HSE Fire Safety in Construction (HSG168)
• CDM 2015

Gas detector calibration protects lives – and keeps you legally compliant.

Gas detection units (GDUs) are essential for identifying hazardous atmospheres – but their accuracy degrades over time. If not properly calibrated, detectors can give false readings or fail to trigger alarms at dangerous gas levels. In this guide, we’ll explain what GDU calibration is, how often it’s required, and what UK law expects from responsible employers.

Regular gas detection unit (GDU) calibration ensures your detectors respond accurately to gas hazards and supports your legal responsibilities under UK health and safety law.

Here’s what this guide covers:

What Is a Gas Detection Unit (GDU)?

A GDU is a fixed or portable device designed to detect harmful levels of gas – including flammable, toxic, and oxygen-deficient atmospheres.

Use cases include:

• Confined spaces (e.g. tanks, voids, basements)
• Manufacturing and industrial plants
• Laboratories and cleanrooms
• Waste, utilities, and energy sites
• Engine test cells and plant rooms

Accuracy is critical. Even a functioning detector may give false confidence if not properly calibrated.

What Does GDU Stand For?

GDU stands for Gas Detection Unit. The term is commonly used to describe fixed gas detectors and gas monitoring devices used to identify hazardous atmospheres before they become dangerous to people, property or operations.

Depending on the application, a GDU may monitor oxygen depletion, flammable gases, toxic gases or refrigerant leaks. These systems are commonly installed in plant rooms, manufacturing facilities, laboratories, utilities infrastructure and confined spaces.

Why GDU Calibration Matters

Gas sensors degrade over time due to:

• Environmental exposure (dust, temperature, humidity)
• Mechanical impact or vibration
• Sensor ageing and contamination (e.g. silicone vapours)

How Often Should GDUs Be Calibrated?

Calibration frequency depends on:

• Sensor type (e.g. catalytic bead, electrochemical, IR)
• Manufacturer guidance
• Environmental conditions
• Frequency and type of use

✅ If unsure, 6-monthly calibration offers a reliable, defensible minimum for most systems.

What Does GDU Calibration Involve?

Calibration is a formal process where sensors are tested and adjusted using certified calibration gas.

Steps include:

• Applying traceable calibration gas to the sensor
• Zeroing the detector in fresh air
• Checking alarm setpoints and response time
• Adjusting sensor output if necessary
• Issuing a calibration certificate (with expiry and engineer ID)

📋 Velocity Safety uses test gases traceable to national standards and works to manufacturer specs to ensure legal defensibility.

Bump Testing vs Calibration

These are not the same – and only one meets compliance expectations:

❗ A bump test only checks if the sensor reacts – not whether the reading is accurate. It does not replace calibration.

Legal & Safety Requirements

Employers are legally required to maintain and verify the function of gas detection systems under several UK regulations:

• Health and Safety at Work etc. Act 1974 (Sections 2 & 3)
• DSEAR 2002 – Dangerous Substances and Explosive Atmospheres Regulations
• COSHH 2002 – Control of Substances Hazardous to Health
• PUWER 1998 – Provision and Use of Work Equipment Regulations

While these laws don’t specify fixed calibration intervals, failing to calibrate may be seen as a breach of your duty of care – especially if a gas-related incident occurs.

You are expected to:

• Maintain gas detection systems in a safe condition
• Ensure accuracy through regular calibration
• Retain traceable calibration records
• Act quickly on faults, failures, or alarms

Who Is Responsible for Gas Detector Calibration?

Under UK health and safety law – particularly the Health and Safety at Work Act 1974 – the responsibility for GDU calibration falls to the:

• Employer
• Duty holder
• Or person in control of premises or safety systems

In practice, this means:

• Scheduling and documenting calibration
• Following manufacturer guidance or risk-based plans
• Acting on faults or failed accuracy checks

In the event of an incident, the enforcing authority (HSE or local authority) will expect to see evidence that reasonably practicable steps were taken to manage risk – including GDU maintenance.

How Long Do Sensors & GDUs Last?

Typical gas sensor lifespan: 2 – 5 years, depending on:

• Sensor type
• Exposure conditions
• Maintenance and handling

⚠️ Accelerated degradation can occur due to:

• High gas concentrations
• Harsh environments (heat, dust, vibration)
• Contaminants (solvents, vapours, silicone)

Warning signs of sensor failure:

• Slower response time
• Inconsistent zeroing
• Frequent false alarms
• Failed bump tests

Velocity Safety can assess your equipment and advise whether recalibration or sensor replacement is available.

Common Gases Detected & Industries That Use GDUs

GDUs are essential wherever gas or vapour risks are present. Common gases and vapours include:

Common gases and vapours:

• CO (Carbon Monoxide)
• CO₂ (Carbon Dioxide)
• O₂ (Oxygen depletion)
• H₂S (Hydrogen Sulphide)
• CH₄ (Methane)
• VOCs (Volatile Organic Compounds)
• NH₃ (Ammonia)
• NO₂ (Nitrogen Dioxide)

Industries supported:

• Construction & Demolition (confined space entry)
• Utilities & Energy
• Manufacturing & Chemical Processing
• Fuel Storage & Distribution
• Logistics Hubs & Cold Stores
• Laboratories, Cleanrooms & Hospitals

Need Professional GDU Calibration Support?

FAQs

How often should gas detectors be calibrated?

Most fixed GDUs should be calibrated every 6 months. In harsher or higher-risk environments, quarterly calibration may be required to stay compliant and ensure accuracy.

Is gas detector calibration a legal requirement in the UK?

Yes. While the law doesn’t specify exact intervals, regulations like COSHH, DSEAR, and the Health and Safety at Work Act require employers to maintain safe equipment. Regular calibration is the recognised method to prove compliance.

Do portable gas detectors need calibration?

Absolutely. Portable detectors should be bump tested before each use and fully calibrated every 3 – 6 months, depending on use, environment, and manufacturer guidance.

What happens if a GDU fails a bump test?

It must be removed from use immediately. A failed bump test suggests the sensor is no longer reliable – it may need recalibration, servicing, or full replacement depending on the fault.

Does a bump test confirm accuracy?

No. A bump test only checks whether the sensor responds to gas – not if the reading is correct. Only a full calibration can confirm sensor accuracy.

What’s included in a gas detector calibration?

Calibration involves applying a known gas concentration to the sensor, adjusting output if needed, checking alarm thresholds, and issuing a certificate for audit purposes. It ensures both safety and regulatory compliance.

Who is responsible for calibrating GDUs?

The employer, duty holder, or site manager is typically responsible. They must ensure calibration is carried out at suitable intervals and maintain traceable records for inspections or investigations.

What are the calibration requirements for gas detectors?

Gas detectors should be calibrated at intervals based on manufacturer guidance, risk assessment, sensor type and environmental conditions. Employers must be able to demonstrate that gas detection equipment remains accurate, maintained and suitable for the hazards being monitored.

Can I calibrate gas detectors in-house?

In some cases, yes – if you have the right test gas, equipment, training, and manufacturer procedures. However, many businesses choose professional calibration to guarantee accuracy and meet HSE audit expectations.

Resources & Further Guidance

• HSE INDG370 – Brief Guide to DSEAR
• HSE L137 – DSEAR ACOP & Guidance
• PUWER 1998 Overview
• HSE – Maintaining Work Equipment
• COSHH Guidance

Understand how HAV testing protects workers and keeps your business compliant.

This guide breaks down the components of a proper HAV risk assessment – from legal exposure limits and exposure points to testing methods, HAVS health surveillance and control strategies that reduce vibration harm.

Long-term use of vibrating tools can cause permanent nerve damage, yet many workplaces still underestimate the risk. Hand-arm vibration testing helps you understand real exposure levels, prevent harm and support your legal duties under the Control of Vibration at Work Regulations 2005.

In this guide, we’ll explain what HAV testing involves, how exposure points work, when health surveillance is needed, and how Velocity Safety delivers accurate on-site hand-arm vibration assessments.

Here’s what this guide covers:

What is Hand-Arm Vibration (HAV)?

Hand-Arm Vibration refers to the vibration transmitted into a worker’s hands and arms when using tools like breakers, grinders, drills, and strimmers.

Prolonged exposure can cause:

• Numbness or tingling in the fingers
• Loss of strength or coordination
• Vibration White Finger
• Hand-Arm Vibration Syndrome (HAVS)

HAVS is a serious, irreversible condition – but it is entirely preventable with proper risk management.

Why HAV Testing Matters

The Control of Vibration at Work Regulations 2005 (enacted under the Health and Safety at Work etc. Act 1974) require employers to:

• Assess vibration exposure
• Control risks wherever reasonably practicable
• Monitor exposure and review controls regularly
• Introduce health surveillance where required

HAV testing helps you generate the exposure data needed to comply with these duties – and reduce the risk of enforcement, claims, or harm.

Who Is at Risk?

HAV risks exist in any setting where vibrating tools are used frequently. High-risk sectors include:

• Construction & Civil Engineering
• Rail & Infrastructure
• Manufacturing & Assembly
• Grounds & Landscape Maintenance
• Utilities & Local Authority Works
• Facilities Management

Even occasional use of high-vibration tools can exceed legal thresholds – especially where workers rotate across jobs.

What is a Hand-Arm Vibration Test?

A HAV test measures the vibration magnitude of a tool (in m/s²) and combines it with usage duration to calculate daily exposure points.

Used to:

• Quantify vibration exposure per task or tool
• Identify high-risk equipment or jobs
• Set safe trigger times using HSE’s ready-reckoner

How Do Exposure Points Relate to a HAVS Risk Assessment?

HAV exposure points are a simple way to compare different tools, trigger times and tasks against the legal exposure thresholds.

The calculation uses two main pieces of information: the vibration magnitude of the tool and how long the worker uses it during the day. Higher vibration levels and longer trigger times create more exposure points.

In a HAV risk assessment, exposure points help you decide whether action is needed, whether trigger times must be reduced, and whether workers may need health surveillance.

• 100 exposure points is equal to the Exposure Action Value.
• 400 exposure points is equal to the Exposure Limit Value.
• If a worker uses several vibrating tools in one day, the exposure points are added together.

The HSE hand-arm vibration calculator helps estimate daily exposure from tool vibration magnitude and usage time.

Legal Limits: EAV vs ELV Explained

Under UK law, two key thresholds apply (measured as an A(8) average over an 8-hour day):

How HAV Testing is Carried Out

Velocity Safety follows industry-standard testing by:

• Attaching a calibrated accelerometer to the tool
• Measuring real-time vibration magnitude during use
• Recording daily usage duration (trigger time)
• Calculating exposure points using the HSE’s ready reckoner

Each test identifies:

• The tool’s vibration level
• How long it can be safely used
• Whether it falls into green (low), amber (moderate), or red (high risk) bands

What Equipment Is Used for HAV Testing and Monitoring?

HAV testing and HAV monitoring are related, but they are not exactly the same thing.

Professional HAV testing uses calibrated vibration measurement equipment to measure the actual vibration magnitude of tools during normal use. This helps create reliable exposure data for your risk assessment.

HAV monitoring equipment, such as exposure timers or tool-use tracking systems, can then help sites manage day-to-day usage, trigger times and worker exposure.

Common equipment includes:

• Calibrated hand-arm vibration meters
• Tool-mounted accelerometers
• HAVi or similar exposure timers
• Software-based exposure calculators
• Digital tool and user reporting systems

Monitoring equipment can support compliance, but it should be based on accurate vibration data. A timer alone cannot tell you whether a tool is safe unless the vibration magnitude used in the calculation is reliable.

Do You Need HAVS Health Surveillance?

Yes – if workers are regularly exposed above the EAV, the 2005 Regulations require you to implement Health Surveillance.

⚠️ Even if HAV testing is carried out, you still need surveillance if exposure levels demand it.

When Should You Re-Test?

HAV testing should be repeated:

• When new tools, accessories, or attachments are introduced
• After health concerns or health surveillance identification
• As tools age (vibration levels can increase over time)
• At least annually as part of your vibration management plan

HAV Risk Assessment FAQs

Here are answers to common questions about HAV testing, vibration exposure points, HAVS health surveillance and employer duties under the Control of Vibration at Work Regulations 2005.

What is a hand-arm vibration test?

A hand-arm vibration test measures the vibration magnitude of tools used by workers. That data is combined with trigger time to estimate daily exposure and decide whether controls, reduced usage times or health surveillance are needed.

What does EAV mean in HAVS?

EAV stands for Exposure Action Value. For hand-arm vibration, the EAV is 2.5 m/s² A(8), or 100 exposure points. Once this level is reached or likely to be reached, employers must take action to reduce exposure.

What does ELV mean in HAVS?

ELV stands for Exposure Limit Value. For hand-arm vibration, the ELV is 5.0 m/s² A(8), or 400 exposure points. Workers must not be exposed above this daily limit.

How do exposure points relate to a HAVS risk assessment?

Exposure points help convert tool vibration levels and usage time into a daily exposure score. This allows employers to compare real work activities against the EAV and ELV, identify high-risk tasks and set safe trigger times.

How do HAVS calculators help with compliance?

HAVS calculators help employers estimate daily vibration exposure, compare results with legal exposure values and record the evidence used in the risk assessment. They are only reliable if the vibration magnitude and usage time entered are accurate.

How often should HAV monitoring be conducted?

HAV monitoring should be reviewed whenever tools, tasks, materials, accessories or working methods change. Many businesses review exposure data annually as part of their vibration management programme, but higher-risk environments may need more frequent review.

Do anti-vibration gloves reduce HAV exposure?

Anti-vibration gloves should not be relied on as the main control measure for HAV risk. HSE says there is no personal protective equipment that can be shown to reliably reduce hand-arm vibration risk, although gloves may help keep hands warm and protect against abrasion.

Is HAVS health surveillance required?

Health surveillance is required where workers are likely to be exposed above the Exposure Action Value, or where they may be at risk for another reason. HAV testing and health surveillance are separate parts of a complete vibration management programme.

Learn more about our full HAV testing and measurement service.

Resources & Further Guidance

• Control of Vibration at Work Regulations 2005
• HSE – Hand-arm vibration guidance hub
• HSE L140 – HAV Approved Code of Practice (PDF)
• HSE HAV exposure calculator and ready reckoner guidance
• HSE Health Surveillance for HAVS