You have received a KHS request for work environment measurement: how to define the right scope

First, read carefully exactly what the KHS requires

A KHS request may be related to an inspection of the workplace, job categorisation, a change of technology, a new operation, or doubt as to whether the existing assessment of working conditions still corresponds to reality.

The first step is to break down the requirement of the public health authority by job positions and risk factors.

If the KHS requires, for example, an objective assessment of noise for press operators and of chemical substances for a paint shop worker, it is not advisable to order a general "work environment measurement". The laboratory must know which job is being assessed, how long the employee performs each activity and which specific factors are to be measured.

The deadline stated in the request is also important. If the scope of the requirement is unclear, it is advisable to clarify it before the measurement begins.

What may be the subject of measurement

Job categorisation is based on Decree No. 432/2003 Coll.. Working conditions are governed in particular by Government Decree No. 361/2007 Coll. and, for noise and vibration, by Government Decree No. 272/2011 Coll..

In regular production operations, the following are most often addressed:

The KHS need not require all the factors present at the workplace. The scope is defined according to the specific job, the previous categorisation and the content of the request.

The basis is a properly described job position

When categorising, Act No. 258/2000 Coll. requires stating the results of the assessment of the employee's exposure to the individual decisive factors in a characteristic shift, including the duration of exposure.

This means that the job title alone is usually not sufficient.

For example, a worker designated as an "assembly worker" may use a pneumatic nutrunner for two hours, perform manual assembly for three hours, drive a handling truck for one hour and inspect products for the rest of the shift.

The scope of measurement must correspond to this actual course of work.

What a characteristic shift is

A characteristic shift is meant to represent the normal working conditions that are decisive for the employee's exposure.

When planning the measurement, we therefore need to know the most frequent work operations that are at the same time significant in terms of exposure.

Noise measurement while part of the production is shut down, sampling of chemical substances on a day with minimal solvent consumption, or measurement of heat stress outside the period when the problem actually occurs may have limited informative value for categorisation.

Conversely, there is no need to create an artificial extreme that does not occur in normal operation.

One job position may require several types of measurement

A common misconception is assigning one risk factor to one employee.

A paint shop worker may be exposed to solvents, noise and physical load at the same time. A grinder may be exposed to noise, hand-transmitted vibration and dust. A worker at a furnace may have significant heat stress and physical load at the same time.

For each position, write down the work activities, their duration, the machines used and the chemical substances. The scope of measurement is determined by the actual work and the KHS requirement.

Chemical substances: send safety data sheets in advance

For chemical factors, it must be determined in advance which specific substances are to be analysed.

A safety data sheet may contain several solvents, acids, metals or other components. The selection is made according to composition, quantity used, volatility, method of application, toxicological properties and hygiene limits.

For painting, for example, it may not be only the component with the highest percentage that is decisive. A minor component may have a significantly stricter PEL.

For chemical substances, categorisation is carried out on the basis of concentrations measured in workplace air in the employee's breathing zone. One of the criteria for the second category is a full-shift average above 0.3 PEL while neither the PEL nor the ceiling permissible concentration (NPK-P) is exceeded. For mixtures and substances with special hazards, further rules apply; the ratio to the PEL alone is therefore not sufficient.

We describe this issue in more detail in the article Measuring solvents and VOC in workplace air: how to select substances from safety data sheets.

Noise: the number of workplaces need not match the number of employees

For categorisation, exposure to a specific job is assessed. If ten employees perform the same activity under comparable conditions, it may not be necessary to carry out ten separate identical measurements.

Conversely, one worker alternating between several significantly different workplaces may require several partial measurements and a subsequent calculation of full-shift exposure.

For noise, Decree No. 432/2003 Coll. lays down, for example:

For impulse noise, the peak level L_Cpeak is also assessed.

Before the measurement, it is therefore important to describe which machines the worker operates and how long he or she actually spends at them during the shift.

Vibration: the actual time the tools are used is important

For hand-transmitted vibration, the time spent working with individual tools is often a significant input.

The information "the worker uses a grinder for eight hours" may be considerably inaccurate if the grinder is in fact switched on only during short work cycles.

Similarly, for a forklift driver, the time of actual driving and the operating conditions are assessed, not automatically the entire length of the shift.

Before the measurement, it is therefore advisable to carry out at least an indicative time study of the work operations.

Heat and cold stress require the right timing

Some factors cannot be objectively assessed at just any time.

If the KHS requires documentation of summer heat stress in a hall influenced by outdoor temperature, a measurement in November will not provide a representative result. Conversely, for an unheated hall, the winter period may be decisive for cold stress.

The situation is different for a technologically heated or cooled space, for example at a furnace or in a freezer room. There, conditions may be reproducible practically all year round.

If a request includes a season-dependent factor and the set deadline cannot objectively be met, it is advisable to discuss the procedure with the relevant KHS in good time.

Physical load and working posture may require a different approach

For the factors physical load and working posture, the Act allows, in certain cases, the use of an expert assessment carried out by the holder of the relevant authorisation in work physiology for classification into the second category.

The protocol must contain, among other things, the nature of the work, the place and time of its performance, shift pattern, the material handled, the work regime, the tools used and the rotation of employees between job positions.

An expert assessment under this procedure cannot be used to remove a job from the category of risk work. Where an occupational disease is recognised or there is a threat of an occupational disease for these factors, the employer must submit a measurement protocol for the job concerned within six months of the recognition.

It is therefore advisable to determine the scope in advance according to the specific work operations and the purpose of the assessment.

Can everything be measured in one day?

Some measurements can be combined. It depends on the scope, the operation and the measurement conditions.

Noise, vibration, chemical substances and some other factors can, with a well-prepared operation, be coordinated within a single measurement day. With a larger number of job positions, several shifts may be needed.

A separate date may be required in particular for heat or cold stress, seasonal work, products manufactured only on certain days, or technological operations that cannot be started simultaneously.

The aim is not to take as many samples as possible in one day, but to obtain results that are representative of the employees' actual exposure.

Measurement for categorisation must meet statutory requirements

Under Section 38 of Act No. 258/2000 Coll., the employer may carry out the measurements and examinations necessary for classifying jobs into the second, third or fourth category only through the holder of the relevant certificate of accreditation or authorisation, where this is regulated by legal regulations for the given field.

This is important when ordering measurement solely on the basis of the lowest price. The result must be usable for the purpose for which the KHS requires it.

In addition to the results, the protocol should clearly identify the job position, the work operations, the operating conditions and the duration of exposure.

What the KHS will need for categorisation

The relevant public health protection authority decides on the classification of a job into the third or fourth category. The application is submitted by the employer.

A job is classified into the second category by the employer, who notifies the relevant public health protection authority of the classification.

The documents contain in particular the designation of the job, the workplace, the results of the exposure assessment in the characteristic shift, the length of the shift and the shift pattern, the number of workers and the measures taken. Depending on the situation, measurement protocols or expert assessments are also enclosed.

It is therefore advantageous to prepare the scope of measurement with the subsequent categorisation in mind. Finding out afterwards that the protocol lacks another work operation or a decisive factor may mean a new site visit.

What to send us when a KHS request arrives

To determine the correct scope, you can send us:

• the entire request, the inspection report or other statement of the KHS, the current job categorisation and any older measurement protocols,
• a list of job positions, numbers of employees, shift lengths, a description of work operations and photographs of the workplaces,
• safety data sheets of the chemical substances used, a list of machines and tools, and information on extraction and on technological sources of heat or cold.

We will first go through the request and documents with you. We will specify the job positions, risk factors and necessary measurements that NATURCHEM can provide, and point out where the holder of another relevant authorisation is needed for an expert assessment or measurement. At the same time, we will determine which measurements can be combined into one date and which require a specific operating or climatic state.

This can prevent the ordering of unnecessary measurements and the situation where, after the results have been submitted, the public health authority asks for another factor or work operation to be added.

You will find more information on the page Work environment measurement – NATURCHEM.

Related legal regulations

Act No. 258/2000 Coll., on the Protection of Public Health

Decree No. 432/2003 Coll., on the conditions for classifying jobs into categories

Government Decree No. 361/2007 Coll., laying down conditions for the protection of health at work

Government Decree No. 272/2011 Coll., on the protection of health from the adverse effects of noise and vibration