Hazardous Area Scales: ATEX Zones, Ratings and Choosing Safely

Hazardous area scales are weighing instruments built or certified so they cannot ignite a flammable gas, vapour or dust cloud. To pick one, you need to know three things: the zone where it will sit, the gas or dust group and temperature class of your material, and whether the complete weighing system, not just the platform, carries the right certification. This guide explains each step in plain terms, so you can specify the right equipment or ask the right questions of a supplier.

TL;DR

• A hazardous area is one where an explosive atmosphere may occur in amounts that need special precautions. Your employer risk assessment decides the zone, and the zone decides the equipment category.

• “Explosion proof” (containment) and “intrinsically safe” (limited electrical energy) are different protection methods. Intrinsic safety is typically used in Zones 0, 1 and 2.

• The whole system must be assessed together: scale base, load cells, junction box, barrier and indicator. Joining several certified parts does not make a certified system.

• For combustible or hazardous powders, controlling dust comes first: enclosure, extraction and cleaning. The scale is one part of the safe set-up.

• Installation, earthing, inspection and calibration need competent people and should follow the manufacturer’s documentation.

Table of Contents

• What makes a weighing area hazardous

• ATEX zones explained

• What ATEX means for scales sold in the UK

• Intrinsically safe or explosion-proof?

• Check the complete system, not the label on one part

• Capacity, accuracy and practical features

• Weighing hazardous powders and combustible dusts

• Installing and maintaining hazardous area scales

• Find the right scale for your task

• FAQ

• Sources

What makes a weighing area hazardous

A hazardous place is one where an explosive atmosphere may occur in quantities that call for special precautions. Typical weighing locations include solvent dispensing rooms, chemical and pharmaceutical powder suites, paint and coatings production, flour and sugar handling, fuel and gas-related plant, and some recycling and woodworking operations.

Two things must be present for an explosion: a flammable substance mixed with air in the right proportion, and a source of ignition. A scale is an electrical device, so it could be that ignition source through a spark, a hot surface or stored electrical energy. Hazardous area scales are designed to remove that possibility.

ATEX zones explained

In Great Britain, employers must assess explosion risks, classify hazardous areas into zones and control ignition sources under DSEAR 2002, as set out in the HSE guidance on classification of hazardous areas. The zones describe how often, and for how long, an explosive atmosphere is present.

The zone definitions come from the HSE document above. The dust-category pairing (1D for Zone 20, 2D for Zone 21, 3D for Zone 22) is set out in this DSEAR explainer. The higher the likelihood of an explosive atmosphere, the more stringent the protection, and Category 1 equipment is generally required for Zone 0 and Zone 20, according to the same HSE guidance.

The zone is not something a scale supplier assigns. It comes from your own DSEAR risk assessment, ideally recorded in a hazardous area classification drawing. If you do not have one, that is the first job before any purchase.

What ATEX means for scales sold in the UK

ATEX is the shorthand for the framework controlling explosive atmospheres and the standards for equipment used in them. The HSE glossary explains that it rests on two pieces of law: DSEAR 2002 protects workers, while the 2016 equipment regulations govern product safety.

The Equipment and Protective Systems Regulations 2016 (SI 2016/1107) put the revised EU ATEX Directive 2014/34/EU into UK law, replacing the 1996 Regulations without changing the technical requirements. HSE explains that manufacturers and suppliers placing equipment on the GB market must meet the essential requirements, follow the appropriate conformity procedure, and mark the equipment with the conformity mark and the Ex symbol.

The applicable conformity mark (UKCA or CE) depends on the product legislation and where the equipment is placed on the market. Check the current position on the HSE and GOV.UK pages when you buy, because marking rules have been adjusted more than once since Brexit. Northern Ireland follows different arrangements again.

Older equipment is treated differently. HSE states that equipment already in use before July 2003 can stay in use indefinitely, provided a risk assessment shows it remains safe to operate.

Intrinsically safe or explosion-proof?

People search for “explosion proof scales” and “intrinsically safe scales” as if they were the same thing. They are different protection concepts.

• Explosion-proof (flameproof, Ex d): the enclosure is built to contain an internal explosion and stop it igniting the atmosphere outside. These tend to be heavy, enclosed units.

• Intrinsically safe (Ex i): the circuit is designed to limit electrical energy so that ignition is not possible, even under fault conditions. The UKWF handbook notes that intrinsic safety is typically suitable for Zones 0, 1 and 2, while other methods depend on the zone and hazard level.

For weighing, intrinsic safety is common because load cells produce very small signals and the platform can stay light and easy to clean. The electronics that supply the power sit in the safe area, behind a barrier.

Which protection suits which job

This table is a guide to the usual logic. The final choice belongs in your risk assessment and the manufacturer’s certificate.

Check the complete system, not the label on one part

This is where most purchasing errors happen. The UKWF handbook says the entire weighing system must be assessed for compliance, by checking certificates against the zone, the gas or dust group and the temperature class. Load cells, junction boxes and safety barriers must be verified as a compatible unit in a verification dossier. It also describes as a common misconception the idea that connecting several ATEX-certified components automatically gives a compliant system.

Before you buy, collect these details:

1. Zone and category: for example Zone 21 needs Category 2D.

2. Gas or dust group: IIA, IIB or IIC for gases, IIIA, IIIB or IIIC for dusts. The group describes how easily the material ignites.

3. Temperature class: the maximum surface temperature of the equipment must stay safely below the ignition temperature of your substance. For dust layers, allow for the layer’s own ignition behaviour.

4. Ingress protection: an IP rating suited to dust and to washdown if you clean with water.

5. Documentation: certificates, instructions and the entity parameters of each component. The ATEX Directive requires manufacturers to supply instructions that let you decide whether an item can be used safely in the intended area, as the Directive text summarises.

Capacity, accuracy and practical features

Certification gets the scale into the room. The weighing task decides which scale is actually right.

• Capacity and readability: choose a capacity that covers your heaviest container including its tare, and a resolution fine enough for your tolerance. A drum-filling task and a small additive dosing task need very different instruments.

• Platform size and format: floor scales and pallet scales suit drums, IBCs and sacks. Bench scales suit smaller pots and jugs.

• Washdown and materials: stainless steel and sealed enclosures help in food, chemical and pharmaceutical settings where equipment is cleaned regularly.

• Display and operation: a clear, large display, and a position for the indicator outside the zone where possible, make operators more accurate.

• Portability: if the scale moves between locations, confirm that every location has the same or a lower classification than the equipment rating.

• Calibration: plan for calibration weights and a service schedule from the start.

If your process does not actually involve a classified area, a standard industrial scale may be all you need. Our range covers platform, floor and precision scales for those applications, and the zoning step above tells you which category you are in.

Weighing hazardous powders and combustible dusts

Searches such as “hazardous powder weighing” cover two related hazards: dust that can explode, and dust that harms health. Both are controlled mainly by how you handle the material, not by the scale.

HSE’s general dust guidance, EH44, lists weighing loose powders among activities that can create dust. It sets out a hierarchy: eliminate the substance, use a safer form (for example a paste instead of a powder), change the process to emit less, enclose it, extract emissions near the source, reduce the number of exposed workers, apply administrative controls, and use personal protective equipment as the last resort. It also says PPE should only be considered once other reasonably practicable measures have not achieved adequate control.

For combustible dust specifically, HSG103 advises that where local exhaust ventilation controls dust release, you may need to interlock the process so it runs only when the ventilation is working. It also says to avoid features such as conveyors that tip into open-topped plant, and bulk discharge from big bags where displaced air comes straight into the workroom.

For mineral powders containing silica, HSE’s MN1 guidance recommends enclosing transfer and weighing as far as possible, using LEV, and providing respiratory protective equipment with an assigned protection factor of at least 40 unless air sampling shows lower protection is adequate. It adds fit testing for tight-fitting masks, clean-shaven wearers, and powered or airline equipment for use beyond an hour. It also recommends synthetic coveralls that do not retain dust and suitable gloves.

The Engineers Ireland analysis of bakery dust explosions makes a useful point for food businesses: the flour dust exposure limit of 1 mg/m3 is far below the lower explosive limit, so health controls such as extraction or containment booths at sieving, weighing and bag emptying also need to be part of the explosion risk assessment.

In practice, a good powder-weighing station combines an enclosed or extracted weighing position, a scale rated for the dust zone if one applies, easy-clean surfaces, and a cleaning routine that never lets dust layers build up.

Installing and maintaining hazardous area scales

Good equipment can still be made unsafe by poor installation. The UKWF handbook says intrinsically safe weighing circuits must use approved safety barriers or switch amplifiers to separate the safe and hazardous areas, and that all components must be grounded correctly for potential equalisation.

A sensible routine looks like this:

1. Keep the manufacturer’s certificate, drawings and instructions with the system record.

2. Have installation and any cable changes done by someone competent in explosive atmosphere work.

3. Do not swap in a cable, load cell or indicator that is not on the verified system documentation.

4. Inspect the equipment at intervals set by your risk assessment, looking for damage, corrosion, loose glands and missing seals.

5. Calibrate with certified calibration weights at the interval your quality system requires, and record each result.

6. Review the zone classification whenever the process, material or layout changes.

HSE’s inspection approach for major hazard sites, in the COMAH electrical, control and instrumentation guide, assesses hazard and risk, design, operation and maintenance, and competence. Those same four themes are a handy checklist for any site.

Our perspective

A hazardous area purchase is rarely about the scale alone. It is about matching a weighing task to a zone, a material and a verified set of components, and then keeping the instrument accurate for years. We see customers save the most time when they arrive with their zone, material group and capacity written down.

We supply more than 3,000 scales and measuring products, from kitchen and personal scales to industrial platforms and precision balances, together with calibration weights and accessories. That breadth lets us help you separate the tasks that sit inside a classified zone from the many that do not, and point you to the right category of instrument for each. Our team can be reached through several channels, so if you are unsure what to specify, ask us before you order.

Anders

Find the right scale for your task

If you are weighing in a standard industrial, laboratory, food or warehouse setting, we stock platform and pallet scales, parts-counting scales, washdown-suited scales, precision and analytical balances, and the calibration weights to keep them accurate. Browse the True-Precision range or contact our customer support team with your capacity, accuracy and environment, and we will help you narrow the options.

For an area classified under DSEAR, give us your zone, gas or dust group and temperature class when you get in touch, so the conversation starts from the right facts.

FAQ

What is the difference between ATEX zones 0, 1 and 2?

They describe how often an explosive gas or vapour atmosphere is present. Zone 0 means continuously or for long periods, Zone 1 means likely in normal operation, and Zone 2 means unlikely in normal operation and short-lived if it occurs. Dust uses the matching Zones 20, 21 and 22, as in the HSE zoning guidance.

Are explosion-proof and intrinsically safe scales the same?

No. Explosion-proof designs contain an internal explosion within a strong enclosure. Intrinsically safe designs limit electrical energy so ignition cannot occur, even with a fault. Which one suits you depends on the zone and the substance.

Can I use any ATEX-certified indicator with an ATEX-certified platform?

Not automatically. The complete system, including load cells, junction box and barrier, must be assessed and verified as a compatible unit against your zone, group and temperature class. Ask the manufacturer for the system documentation.

Who decides which zone my weighing area is in?

You do, as the employer, through your DSEAR risk assessment. A scale supplier can advise on equipment, but the classification belongs to the site and should be reviewed when processes or materials change.

Sources

• HSE: Classification of hazardous areas (zoning)

• HSE: ATEX and explosive atmospheres

• HSE: Equipment and machinery glossary

• The Equipment and Protective Systems Regulations 2016 (SI 2016/1107)

• ATEX Directive 2014/34/EU summary

• DSEAR 2002 explained: UK employer guide

• UKWF Handbook: Controlled Applications

• HSE EH44: Dust in the workplace

• HSE HSG103: Safe handling of combustible dust

• HSE MN1: Weighing mineral powders containing silica

• Engineers Ireland: Dust explosions in bakeries

• HSE COMAH electrical, control and instrumentation guide