ATEX industrial filtration design

IF VERY fine dust particles generated during the manufacturing process are dispersed into the air, they may catch fire and/or cause an explosion. Across Europe, employers are required to demonstrate that appropriate measures are in place to prevent explosions, or protect against or mitigate their effects. In the EU, these obligations are set out in the ATEX Workplace Directive (Directive 1999/92/EC), while they are implemented through the Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) enforced by the Health & Safety Executive (HSE) in the UK. Both frameworks establish a clear hierarchy of measures, whereby explosion prevention is preferable to explosion protection and mitigation. 

The core ATEX philosophy is to avoid the formation of an explosive atmosphere in the first place. However, for many manufacturing processes this is not always feasible, so the focus shifts to identifying and controlling potential ignition sources wherever possible. Where this cannot be fully achieved, explosion protection and mitigation measures must be implemented to limit and control the effects of an explosion. Typical mitigation measures used in dust filtration systems include explosion venting, flameless venting and explosion isolation devices.

The process owner must identify the different zones within their plant and inform their industrial filtration supplier so that they provide equipment within the correct category. In addition to selecting the correct ATEX equipment category, industrial filtration equipment suppliers must also consider other aspects, such as:

- Ingress protection (IP) rating: the degree of protection that enclosures provide against the ingress of solid foreign objects and water.

- Surface temperature: equipment must be marked with a maximum permissible surface temperature.

- Static electricity: measures must be taken to prevent hazardous discharges of static electricity.

- Marking – equipment must be clearly marked with the appropriate explosion protection marking (Ex symbol), together with the group, category and temperature class.

Combustible dust mitigation strategy considerations

The creation of a mitigation plan by the process owner to help manage combustible dust is required for all facilities. Key considerations include:

Prevention measures - Equipment operators must be trained on the explosion hazards associated with combustible dusts and the measures implemented to control them. 

Dust control measures - Dust-containing systems, including ductwork and dust collectors, should be designed so that fugitive dusts are not allowed to accumulate in the work area. The facility must have a housekeeping programme to minimise dust accumulations within the facility. Working surfaces should be designed to minimise dust accumulation and to facilitate cleaning. Proper maintenance and regular inspection of any equipment in contact with potential explosive atmospheres must be undertaken, according to its specific risk assessment. All inspection, maintenance and cleaning instructions specified in the dust collector manufacturer’s manual must be followed.

Ignition control measures - The facility should have an ignition control programme that addresses potential ignition sources associated with dust-handling operations. Duct systems, dust collectors and dust-producing machinery should be bonded and earthed to minimise the accumulation of static electrical charge. 

Protection measures - The facility must maintain an explosion protection document, including an assessment of specific explosion risks relevant to its activities. Dust collectors should preferably be located outdoors. However, indoor installation is also feasible if appropriate explosion protection and mitigation measures are applied correctly.

Where explosion venting is used on dust collectors, venting devices should be positioned to safely relieve explosion pressure to an appropriate location away from personnel. In cases where discharge to the outside is not possible or practical, flameless venting solutions should be applied to allow pressure relief while preventing the release of flames into the surrounding area. In more extreme cases, chemical suppression solutions can also be implemented, which stops the explosion at source. An experienced supplier of dust collection equipment will be able to provide the most appropriate explosion protection method. Where dust-handling equipment is interconnected by ductwork, suitable isolation measures should be considered to prevent the propagation of an explosion between system components.

Balanced approach

Selecting the appropriate industrial filtration system for combustible dust environments in manufacturing plants requires a systematic approach that balances regulatory compliance, detailed risk assessment, and appropriate equipment selection and design.

Process owners must conduct an explosion risk assessment to classify hazardous areas into ATEX zones. This information forms the basis for the selection of suitable equipment and protective measures. Testing by a qualified laboratory should also be undertaken to determine the dust's explosion characteristics, helping to characterise the explosion hazards associated with the dust. Separately, filtration equipment manufacturers are responsible for assessing potential ignition sources within their equipment in accordance with the applicable EN standards. The selected filtration equipment must be suitable for the designated ATEX zone and the explosion hazards identified by the risk assessment.

It is not always practicable to eliminate the presence of a potentially explosive atmosphere or all possible ignition sources. In such cases, the dust collection system should incorporate appropriate explosion protection and mitigation measures to limit the consequences of an explosion and support safe operation.

(Please note, the information in this article is provided for general guidance only and should not be considered legal, regulatory, or technical advice.)

Melisa Diaz is product compliance engineer, and Richard Jones is sales manager at Donaldson

www.donaldson.com