Laser classes 1 to 4: what the classification means for day-to-day operation

The class says nothing about the quality or the capability of a machine. It describes how hazardous the accessible radiation is for eyes and skin. The duties follow from this classification: demarcation of the area, protective equipment, instruction, and in the higher classes also the appointment of a laser safety officer.

This article sets out the classes, explains why cleaning lasers regularly end up in the highest one and shows what that means in practice. What is actually required in your business follows from the risk assessment.

What the classification is for

Classification under the product standard EN 60825-1 assigns laser equipment to classes on the basis of the accessible radiation. It is addressed first of all to the manufacturer: they have to classify their machine, mark it and fit it with the required protective devices.

For the operator the class is the entry point to the risk assessment. It does not replace that assessment — circumstances at the specific workplace may require additional measures — but it sets the framework below which no argument is possible.

The direction of view matters: what is classified is what is accessible. A powerful laser in a tight, monitored enclosure can carry a lower class than the same laser source without a housing.

The classes at a glance

The standard knows more than the four numbers commonly heard. In order, from the lowest to the highest hazard:

• Class 1 — not hazardous under the intended conditions
• Class 1M — not hazardous as long as no optical instruments are used
• Class 1C — for application directly to tissue, with particular requirements
• Class 2 — visible range, protection by the blink reflex
• Class 2M — as 2, but not when optical instruments are used
• Class 3R — limit values may be exceeded, risk comparatively low
• Class 3B — hazardous to the eye when looking directly into the beam
• Class 4 — hazardous even as a diffuse reflection, plus skin and fire risk

For industrial cleaning only classes 1 and 4 are relevant in practice — the one for fully enclosed installations, the other for everything that is hand-guided or works in the open.

Class 1 and 1M: safe under defined conditions

Class 1 does not mean "weak laser". It means the accessible radiation presents no hazard under the intended operating conditions.

This can be achieved in two ways: through genuinely low power — or through an enclosure that safely contains the beam and switches the laser off when opened. The second route is the usual one in production. An installation of several kilowatts can be placed on the market as a class 1 product if the housing and interlocking allow it.

Class 1M carries an M for "magnifying optics": without binoculars or a magnifier the radiation is not hazardous, with such instruments it is. In laser cleaning this hardly plays a role.

Class 2 and 2M: visible and reliant on the blink reflex

Class 2 applies only to visible radiation between roughly 400 and 700 nanometres and to low powers. The protection rests on the fact that with such a bright source one involuntarily blinks and looks away.

Typical examples are laser pointers, levelling devices and pilot lasers. Cleaning lasers do not come under this — if only because their working wavelength lies in the invisible infrared. Where there is nothing to see, there is no blink reflex either.

This distinction is why experience with a construction laser cannot be transferred to a cleaning laser.

Class 3R and 3B: hazardous when looking into the beam

From class 3R the exposure limit values may be exceeded. The risk of injury is regarded as comparatively low here because the power is limited — it becomes hazardous when looking directly into the beam.

Class 3B is considerably more serious: looking directly into the beam is hazardous, as is looking at specular reflections. Diffuse reflections from matt surfaces are, by contrast, generally uncritical.

From class 3R the obligation to appoint a laser safety officer applies. Safety eyewear, a demarcated area and instructed personnel are likewise required from here on.

Class 4: diffuse reflection becomes hazardous too

Class 4 is the highest classification. Three points distinguish it from everything below:

1. It is not only the direct or specularly reflected beam that is hazardous, but also the diffuse reflection from matt surfaces.
2. Besides the eye, the skin can be injured.
3. There is a fire risk — the radiation can ignite combustible substances.

The first point has the greatest practical significance. With class 3B it is enough not to look into the beam. With class 4 avoiding the beam is not enough: someone standing beside the working point and looking at the workpiece can be at risk too. That is why the laser area is larger with class 4 and has to be demarcated, and why bystanders also need protection.

Why cleaning lasers fall into class 4

To remove rust, paint or oxide layers, enough energy has to be brought onto the surface to release the layer. The power levels usual for this lie well above what class 3B covers.

Then there is the design. A hand-guided machine is built for mobility — it is meant to reach components that cannot be placed in a chamber. That very property rules out the enclosure through which a lower class would be attainable.

The classification is therefore not a peculiarity of a particular manufacturer but a consequence of task and design. An offer that states a lower class for a hand-guided machine of several hundred watts should prompt a query.

Enclosed installations and the matter of class 1

In series production, laser cleaning is often automated: the laser sits in a cabin, a robot or an axis system guides it, doors are interlocked.

Such an installation can be classified as class 1 even though a class 4 laser source works inside it. The protection then comes not from personal equipment but from the design.

Two things have to be borne in mind. First: the classification applies only as long as the enclosure is intact and the interlocking effective — for maintenance and set-up work with the housing open, the requirements of the higher class apply again. Second: interlocks have to be tested at recurring intervals. A bridged door switch puts the entire protection out of action.

What class 4 means for day-to-day operation

A number of requirements follow from the classification which should be in place before the first start-up:

• Define, demarcate and mark the laser area; prevent access by uninvolved persons
• Appoint a laser safety officer in writing, with proof of expertise
• Safety eyewear matching wavelength, mode of operation and power, for everyone in the area
• Draw up the risk assessment, including process emissions and fire loads
• Instruction before work begins and regularly thereafter
• Extraction and filtration, because particles and fumes are produced during ablation
• Warning light or comparable indicator that makes laser operation recognisable

With mobile assignments there is the added point that the laser area has to be defined afresh for each place of work. This is the point most often underestimated when working at a customer's premises.

Fire risk is often underestimated

Of the three characteristics of class 4, fire risk gets the least attention — yet it is the one most likely to cause material damage.

When paints and coatings are removed, particles and fumes are produced that can be combustible. If the beam strikes combustible material in the vicinity, that can be enough. Filters and extraction systems are a point too: dust deposited in the filter can ignite under unfavourable circumstances.

The assessment therefore covers the surroundings of the workplace, the design of the filter system and the question of what happens if the machine is not switched off at the most unfavourable moment. When working on other companies' premises it also has to be clarified whether a permit for hot work is required.

What has to appear on the machine

A machine properly placed on the market carries marking from which the laser class is evident, together with details of wavelength and power. Operating instructions in the language of the country and the declaration of conformity belong with it.

If these details are missing or contradictory, the risk assessment cannot be set up soundly — nor can the procurement of matching safety eyewear. With direct imports and second-hand purchases this is, in experience, the most frequent stumbling block.

Before buying, check whether the rating plate, operating instructions and declaration of conformity are present and consistent with one another. That is done more quickly than clarifying it afterwards.

Sources

• EN 60825-1 — Safety of laser products, equipment classification and requirements — Assignment to the laser classes, marking and requirements for protective devices.
• OStrV — German regulation on the protection of workers from artificial optical radiation — Risk assessment, protective measures, obligation to appoint laser safety officers from class 3R.
• TROS Laser Radiation — Technical rules on the regulation — Assessment of the hazards, exposure limit values, measures to protect employees.
• DGUV — FBHM-139 "Blasting work — cleaning and decoating with laser radiation" — Edition 06/2024. Sector-specific guidance on cleaning and decoating with laser radiation.

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