Respiratory Protective Equipment (RPE) is a particular type of Personal Protective Equipment (PPE), used to protect the individual wearer against inhalation of hazardous substances in the workplace air. This article provides information on definitions, technical requirements and rules of proper selection of various types of respiratory protection equipment i.e. filters, filtering half masks, face pieces, breathing apparatus and filtering escape devices for protection against particles (including nanoparticles), gases, vapours and oxygen deficiency.
The atmosphere of workplaces may contain solid and liquid particles, including nanoparticles, i.e., mists, fibres, radioactive particles, or also vapours, gases and micro-organisms which present serious risks to health. If workers are exposed to harmful levels of hazardous substances in workplace air, their health is at risk, either in the short or long term. Moreover, work activities may be carried out in confined spaces or areas with low oxygen levels (oxygen deficiency, less than 19% by volume). To protect the workers against these health risks employers must carry out a and take appropriate prevention measures. RPE should only be used where adequate control of exposure cannot be achieved by other means. RPE is the last resort following the hierarchy of control measures. Measures to eliminate the hazard at source should always be preferred in order to protect everyone in the workplace. Such measures include e.g. elimination or substitution of hazardous material or a change in the process. Engineering controls and organisational measures (e.g. limiting the exposure time) also have to be considered and implemented if possible. However, if these prevention measures are not efficient or not sufficient for reducing the risks then suitable respiratory protection equipment may be needed. Examples of such hazardous work situations include maintenance activities (e.g. tank cleaning, sludge removal, freezer room repairs), due to the possibility of a sudden release of highly concentrated chemical substances (e.g. organic solvent vapours, trapped process inorganic gases, refrigerant vapours).
The principle that employers should treat RPE (and PPE in general) as a last resort when determining and implementing prevention measures is included in the EU legislation on OSH. Directive 89/656/EEC states "personal protective equipment shall be used when the risks cannot be avoided or sufficiently limited by technical means of collective protection or by measures, methods or procedures of work organization." Other obligations for the employer include:
- supplying RPE to workers free of charge,
- making a proper selection of RPE, depending on the type of hazard,
- determining the conditions of using the RPE,
- organising training,
- ensuring an adequate maintenance, cleaning and disinfection of RPE.
All RPE provided to the workers must also meet the requirements specified in the EU Regulation on personal protective equipment. This regulation contains provisions on the design, manufacture and marketing of PPE. The CE marking affixed to PPE provides evidence of compliance of the product with the legal requirements. The EU Regulation is applicable to all PPE that is placed on the market (not only PPE used in the workplace) and sets out the rules for manufacturers. The CE marking affixed to PPE provides evidence of compliance of the product with the legal requirements. A PPE is subjected to conformity assessment both during the design and production phase. The manufacturer must ensure that the essential health and safety requirements remain fulfilled during the lifetime of the PPE. The presumption of conformity with the essential health and safety requirements is ensured by adherence to harmonised European standards.
Basic rules of RPE use
RPE should be considered as a last resort for preventing and/or controlling exposure to hazardous substances in the air. RPE should only be used after all other reasonably practicable control measures have been taken. Eliminating or reducing risks at the source and/or engineering controls are more effective because RPE only protects individual workers and is prone to failure or misuse, such as wearing the wrong RPE for the job. Furthermore, workers wearing RPE may get a false sense of security when using it.
In general, RPE can be used in the following situations (based on a risk assessment):
- where an inhalation exposure risk remains after reasonable controls have been put in place (residual risk),
- short-term or infrequent exposures when other controls at the source are not reasonably practicable,
- while other control measures (temporary measures) are installed or maintained/repaired,
- emergency escape – it is necessary to provide RPE for a safe exit from an area where hazardous substances may be released suddenly in the event of a control system failure,
- emergency work or temporary failure of controls where other means of controls are not reasonably practicable,
- emergency rescue by trained personnel is necessary.
RPE should not be confused with face masks such as surgical masks used in care facilities. These masks are not considered as personal protective equipment since they do not offer a protection for the user. A surgical mask is a medical device covering the mouth and nose ensuring a barrier to limit the transition of an infectious agent between the caregiver and the patient. Surgical masks fall under the EU Medical Device Regulation 2017/745  and compliancy to this regulation is demonstrated by the CE-mark.
There are two general types of respiratory protective equipment (RPE), based on the principle by which protection is provided to the user. The two types are the following:
- Respirators (filtering equipment) i.e.: filter, gas filter, combined filter, filtering half-mask.
- Breathing apparatus (isolating equipment) i.e.: self-contained breathing apparatus (open-circuit and closed circuit), compressed line breathing apparatus.
Respirators are designed to filter out or clean contaminated air from the workplace atmosphere before it is inhaled by the respirator wearer. Respirators are not designed to be used in atmospheres with oxygen deficiency (concentration of oxygen is below 19%) or where the concentration of unknown contaminants has not been evaluated.
Breathing apparatuses deliver breathable air from an independent source (compressed air vessels, compressed line) to the user. Breathing apparatuses are designed for use in atmospheres with oxygen deficiency (where the concentration of oxygen is below 19%).
General classification of the Respiratory Protective Equipment is as follows:
1. Respirators – filter out contamination from the air in the workplace before it is inhaled by the user:
a. Filtering respirators:
- Filtering face pieces
- Half mask with filter(s)
- Full-face mask with filter(s)
b. Powered/assisted respirators:
- Powered hoods and helmets with filter(s)
- Powered-assisted half mask with filter(s)
- Powered assisted full-face mask with filter(s)
2. Breathing apparatuses – provide uncontaminated breathable air from independent source:
a. Compressed airline breathing apparatuses:
- Constant flow with any type of face piece
- Negative demand half or full-face mask
- Positive demand half or full-face mask
b. Indented line Self-contained breathing apparatuses:
- Open-circuit negative demand full-face mask
- Open circuit positive demand full-face mask
- Closed-circuit full-face mask demand
Moreover, there is a specific group of RPEs, the so-called rescue equipment, with a limited time of protective performance which allows the user to leave the contaminated area in a very short time. It is not applied for constant activities but is merely equipment for workers to use in rooms or buildings where there is a real risk of sudden emergency.
Filtering face pieces: these face pieces are often called “disposable respirators". They either entirely or substantially consist of filter material. They should conform to the EN 149:2001 standard and are classified as FFP1, FFP2 and FFP3 in order of increasing filtration efficiency.
There are two types of these respirators i.e.
- intended to be used for a maximum of a single shift (marked with the letters NR – not reusable), and
- intended to be used for more than a single shift (marked with the letter R – reusable).
The respirators may incorporate inhalation and exhalation valves or exhalation valve(s) only, or have no valves. Where the filtering face piece has no valves, both inhaled and exhaled dangerous substances can pass through the filter material. An example of the filtering face piece is shown in the picture.
There are also valved filtering half masks to protect against gases or vapours and particles. These devices are “disposable" respirators essentially for use against gases and vapours, but with optional protection against particles. Any gas/vapour filters form an inseparable part of the device; any particle filters maybe integral or separable. Complete devices should conform with the EN 405:2001+A1:2009 standard and are designated according to the filter type used and have the prefix FF. The devices must have both inhalation and exhalation valves. Examples of gas/vapour and combined filters are: FFA1, FFB2P3, FFK1P2. There are also two types of these respirators i.e. those intended to be used for a maximum of a single shift (marked with the letters NR – not reusable), and those intended to be used for more than a single shift (marked with the letter R – reusable).
Filters either entirely or substantially consist of filter material. There are particle filters, gas filters and combined filters.
The particle filters should conform to the EN 149:2001 standard and are classified as P1, P2 and P3 in order of increasing filtration efficiency. There are two types of these respirators i.e. intended to be used for a maximum of a single shift (marked with the letters NR – not reusable), and intended to be used for more than a single shift (marked with the letter R – reusable).
The gas filters should conform to the EN 14387:2004+A1:2008 standard and are classified as:
- A - for use against certain organic gases and vapours with a boiling point > 65 °C as specified by the manufacturer,
- B - for use against certain inorganic gases and vapours as specified by the manufacturer.,
- E - for use against sulphur dioxide and other acidic gases and vapours as specified by the manufacturer
- K - for use against ammonia and organic ammonia derivatives as specified by the manufacturer,
- AX - for use against certain organic gases and vapours with a boiling point £ 65 °C as specified by the manufacturer. For single use only,
- SX - for use against specific named gases and vapours as specified by the manufacturer.
Multi-type gas filters - filters which are a combination of two or more of the above listed types, excluding SX, and which meet the requirements of each type separately.
Combined filters - gas or multi-type gas filters incorporating a particle filter according to EN 143:2001.
Special filters are:
- Type NOP3 - for use against nitrogen oxides, e.g. NO, NO2, NOX.
- Type HgP3 - for use against mercury.
There are 3 classes of gas filters for types A, B, E and K that are classified in terms of capacity as follows:
- Class 1- low capacity filters;
- Class 2 - medium capacity filters;
- Class 3 - high capacity filters.
The protection provided by a class 2 or class 3 filter includes protection provided by the corresponding filter of lower class or classes.
The classification of combined filter(s) includes that of particle filter(s) according to EN 143:2000.
Type AX and type SX gas filters and special filters are not classified.
Half masks: usually reusable moulded face pieces, of rubber or plastic, covers the nose and mouth of the wearer and is held in place with adjustable straps. Air passes through the relevant filter(s) by the wearer’s lung force, or may be supplied by a powered unit or suitable breathing apparatus attached to the mask. The exhaled air passes through an exhalation valve(s). Filters are available for particulates, gases or vapours or as a combination. The mask should conform to the EN 140:1998 standard. An example of a half mask in shown in the picture.
Full-face masks: reusable devices that cover the eyes, nose, mouth and chin, and seals against the face of the wearer. It is held in place (on the head) with adjustable straps. Air is drawn into the mask either through a relevant filter(s) by the wearer’s lung force, or may be supplied by a powered unit or suitable breathing apparatus attached to the mask. The exhaled air passes through an exhalation valve(s). Most masks have an inner half mask. Some devices may be equipped with a speech diaphragm to improve the quality and clarity of voice communication. The visor provides protection against particulates and gases.
There are 3 classes of full-face masks:
- Class 1 – light duty design intended for use with a filter(s) and light duty compressed airline breathing apparatus,
- Class 2 – more robust and offers greater resistance to flammability
- Class 3 – for protection against flame and radiant heat. This type is suitable for fire fighting. The mask should conform to the EN 136:1998 standard. An example of a full-face mask in shown in the pictu
Compressed airline breathing apparatuses are intended to be used in heavily industrial applications. The devices rely on a source of clean breathable compressed air at a maximum pressure of 10 bar. Sufficient volume should be available at the source to supply all the devices connected when working at their maximum demand. Some air supply systems also supply air tools such as spray guns. Their consumption should also be taken into account. The air is supplied to the wearer via a tube(s). This tube(s) can be heavy-duty and have good kink and crush resistance with a length determined by the manufacturer. The light-duty construction is used where there is a low risk of damaging the tube in the workplace.
There is a basic subdivision of the types of equipment depending on how the air is used when the compressed air reaches the wearer:
- Constant flow equipment: the usual arrangement for this type of equipment is to connect the compressed air supply tube to a belt-mounted flow control valve or regulator. This supplies air at a constant flow to the face piece via a breathing hose. Face mask (half masks, full face masks) visors and hoods can all be used with constant flow devices, but only as specified by the manufacturer. An example of constant flow equipment integrated with different types of face pieces is shown in the picture.
- Demand valve equipment: here the compressed air is supplied to a demand valve mounted on the mask. This opens as the wearer breathes in, and closes when breathing out. Demand valves can deliver, with certain limits, enough air for a wearer. The valves come in two versions: - Negative demand – this operates as the wearer’s breathing makes the pressure in the mask fall below that outside - Positive demand – where the face mask stays at a pressure slightly above normal.
Both types of demand-type compressed air equipment are normally used with a full-face mask, but it is possible to use half masks. An example of the device is shown in the picture.
Self-contained breathing apparatuses consist of a full-face mask fitted with a demand valve and supplied with clean air from vessels of compressed breathable air. Both negative and positive demand types are available. These devices are the most complex, requiring a high degree of training for both wearing and maintenance. The devices are only likely to be used in potentially very dangerous situations.
Duration of use is dependent on the size and number of compressed air vessels.
- Open-circuit compressed-air devices (exhaled air is discharged to the atmosphere) typically lasts about 60 minutes, and is widely used by industry and emergency staff.
- Closed-circuit compressed-oxygen devices (carbon dioxide in the exhaled air is removed by an adsorbent and the cleaned air is topped up with oxygen and recirculated) can last for more than two hours. An example of a self-contained breathing apparatus is shown in the picture.
Self-contained breathing apparatuses for escape purposes are available in compressed-air, compressed oxygen and chemical oxygen types and are intended to be used for a short-duration in case of an emergency escape from hazardous areas. Escape devices should be used for escape purposes only, and should not be used for normal working or entry to hazardous areas.
As explained above, all RPE placed on the EU market must meet the requirements specified in Regulation 2016/425/EU on PPE . This regulation divides PPE into three categories according to the level of risk. RPE belong to Category III that includes PPE that protect against risks that may cause very serious consequences such as death or irreversible damage to health. To each of these categories different conformity assessment procedures apply. RPE fall into category III PPE. This means that the conformity assessment procedure includes an EU type-examination and product/quality checks by a notified body.
To ensure that the RPE are compliant with the essential health and safety requirements a manufacturer can use harmonised European standards. These standards contain technical specifications, test methods and define performance levels, etc. . The table below provides an overview of the standards.
Table - Harmonised EN Standards - Respiratory protective devices
|EN 136:1998||Respiratory protective devices. Full face masks. Requirements, testing, marking|
|EN 137:2006||Respiratory protective devices. Self-contained open-circuit compressed air breathing apparatus with full face mask. Requirements, testing, marking|
|EN 138:1994||Respiratory protective devices. Specification for fresh air hose breathing apparatus for use with full face mask, half mask or mouthpiece assembly|
|EN 140:1998||Respiratory protective devices - Half masks and quarter masks - Requirements, testing, marking|
|EN 142:2002||Respiratory protective devices - Mouthpiece assemblies - Requirements, testing, marking|
|EN 143:2000||Respiratory protective devices - Particle filters - Requirements, testing, marking|
|EN 144-1:2000||Respiratory protective devices — Gas cylinder valves|
|EN 145:1997||Respiratory protective devices - Self-contained closed-circuit breathing apparatus compressed oxygen or compressed oxygen-nitrogen type - Requirements, testing, marking|
|EN 148-1:1999||Respiratory protective devices — Threads for facepieces|
|EN 149:2001 + A1:2009||Respiratory protective devices - Filtering half masks to protect against particles - Requirements, testing, marking|
|EN 402:2003||Respiratory protective devices - Lung governed demand self-contained open-circuit compressed air breathing apparatus with full face mask or mouthpiece assembly for escape - Requirements, testing, marking|
|EN 403:2004||Respiratory protective devices for self-rescue - Filtering devices with hood for escape from fire - Requirements, testing, marking|
|EN 404:2005||Respiratory protective devices for self-rescue - Filter self-rescuer from carbon monoxide with mouthpiece assembly|
|EN 405:2001 + A1:2009||Respiratory protective devices - Valved filtering half masks to protect against gases or gases and particles - Requirements, testing, marking|
|EN 1146:2005||Respiratory protective devices - Self-contained open-circuit compressed air breathing apparatus incorporating a hood for escape - Requirements, testing, marking|
|EN 1827:1999 + A1:2009||Respiratory protective devices - Half masks without inhalation valves and with separable filters to protect against gases or gases and particles or particles only - Requirements, testing, marking|
|EN 12021:2014||Respiratory equipment — Compressed gases for breathing apparatus|
|EN 12083:1998||Respiratory protective devices - Filters with breathing hoses, (Non-mask mounted filters) - Particle filters, gas filters, and combined filters - Requirements, testing, marking|
|EN 12941:1998||Respiratory protective devices - Powered filtering devices incorporating a helmet or a hood - Requirements, testing, marking|
|EN 12942:1998||Respiratory protective devices - Power assisted filtering devices incorporating full face masks, half masks or quarter masks - Requirements, testing, marking|
|EN 13794:2002||Respiratory protective devices - Self-contained closed-circuit breathing apparatus for escape - Requirements, testing, marking|
|EN 13949:2003||Respiratory equipment — Open-circuit self- contained diving apparatus for use with com- pressed Nitrox and oxygen — Requirements, testing, marking|
|EN 14387:2004 + A1:2008||Respiratory protective devices - Gas filter(s) and combined filter(s) - Requirements, testing, marking|
|EN 14435:2004||Respiratory protective devices - Self-contained open-circuit compressed air breathing apparatus with half mask designed to be used with positive pressure only - Requirements, testing, marking|
|EN 14529:2005||Respiratory protective devices — Self-contained open-circuit compressed air breathing apparatus with half mask designed to include a positive pressure lung governed demand valve for escape purposes only|
|EN 14593:2005||Respiratory protective devices - Compressed air line breathing apparatus with demand valve|
|EN14594:2005||Respiratory protective devices - Continuous flow compressed air line breathing apparatus - Requirements, testing, marking|
To select the most adequate and suitable RPE for the task, it is necessary to conduct a risk assessment. Based on the assessment the selected RPE has to offer an adequate protection to the hazard and to reduce exposure to the level required to preserve the wearer’s health. Furthermore, the RPE has to be suitable for the wearer, task and environment, in such a way that the wearer can work freely and without additional risks due to the use of RPE.
Elements to consider when carrying out the assessment for selecting the RPE are:
- the oxygen levels during the whole period of work/exposure;
- the hazardous substance, their physical and chemical properties and health effects;
- the amount in the air (exposure) and the foreseeable worst-case concentrations, the relevant occupational exposure limit values or safe exposure levels;
- the form of the substance in the air (e.g. gas, particle, vapour, dust, fibre, micro-organism);
- the type of work being carried out;
- other hazards (e.g. potential for splashing, sparks, fire, flammability) associated with the task, which will influence the selection and use of a RPE;
- task requirements regarding mobility, visibility, communication, the use of tools, etc.;
- the duration of wearing RPE;
- any specific wearer requirements, such as other PPE or a need for spectacles.
Standards such as EN 529 Respiratory protective devices - Recommendations for selection, use, care and maintenance (Guidance document) and ISO/TS 16975-1 Respiratory protective devices - Selection, use and maintenance - Part 1: Establishing and implementing a respiratory protective device programme offer guidance for selecting adequate and suitable RPE.
A facepiece (quarter, half and full face mask and filtering half mask) will not provide optimum performance if it leaks. The facepiece provided with a respiratory protective device should fit the wearer properly. However not all wearers are the same. Differences in facial anthropometric dimensions exist between males and females and also racial/ethnic groups. Standard ISO/TS 16976-2 Respiratory protective devices - Human factors - Part 2: Anthropometrics contains anthropometric measurement methods and anthropometric data for head, face, and neck dimensions that manufacturers can take into account when designing RPE. In the workplace fit tests can further ensure a good fit of the mask to the individual.
There are two types of face fit tests - quantitative and qualitative:
- quantitative testing is performed using particle counting monitors or controlled negative pressure devices. From the direct numerical measurement, a calculation of the effectiveness of fit - known as a “Fit Factor" - can be determined,
- qualitative testing is a method based on the tasting or smelling of a bitter, sweet or odorous compound. The method strictly depends on the face piece wearer being able to detect the test compound.
The so-called "tight fitting" RPE should not be used by people whose beard, sideburns or scars, etc. make it impossible to adjust the facial part correctly because this could hinder the proper functioning of any breathing valves.
Prior to every use of a RPE, the following ought to be checked:
- whether the RPE is not damaged;
- whether the respiratory valves are not damaged;
- whether the head tapes allow for tight fitting,
- whether the particle filters, gas/vapour filters or multi-gas filters are in good condition, i.e. individual packaging or casing is not damaged and whether the markings correspond to the identified hazard;
- whether the RPE has expired;
- for power-assisted respirators, it is also necessary to check whether the battery is charged and – according to the producer’s instruction – whether minimum volume concentration of air flow is achieved.
After putting on and adjusting the face pieces, it is necessary to check its tightness. In order to do so, the following ought to be done:
- inlets of filtering elements to be tightly covered by hands,
- facial part is correctly fitted and tight if there is hard resistance while inhaling and the half-mask’s walls come closer to the face,
- inlets of exhale valves to be tightly covered by hands,
- face pieces is correctly fitted and tight if there is hard resistance while inhaling and the half-mask’s walls move away from the face,
- in case of noticing any lack of tightness, the facial part ought to be adjusted again and tightness ought to be checked again,
- in case there is no possibility of obtaining appropriate tightness, the face pieces ought to be exchanged.
Training of the use of RPE
In order to provide the required level of protection, relevant training on how to adequately select, fit, use, maintain and store the RPE is necessary. Training for workers (RPE wearers) should be tailored to the specific RPE intended for use, and to the application to which it will be put. The relevant training should cover both the theory and practice of various types of RPEs to be used, and it will have to be based on the recommendations and instructions supplied by the manufacturer. The content of the training depends on the complexity and performance delivered by the equipment, and on the target work environment in which the equipment will be used. A typical training procedure/programme shall include:
- introduction to hazardous or harmful factors occurring in the working environment;
- explanation of why (a) specific RPE(s) is needed – applying to the work activities and when to use it as well as pointing out the consequences of not doing so;
- explanation of the basic rules related to how it works (what it can and cannot do);
- explanation of how to select appropriate RPE (if more than one type is available);
- selection of the optimum or best type of suitable RPE;
- practice in putting on, wearing and taking off;
- for equipment including a face mask, instruction in achieving the required fitting to the face of the user (fit-checking);
- explanation related to factors which can affect the protection level provided by the equipment;
- pre-use inspection and check of performance, when appropriate;
- practice and instruction in simple user maintenance;
- cleaning and inspection after use;
- correct storage.
Both workers and their supervisors should be aware of the following:
- what are the protective features of the applied RPE;
- what are the consequences of not using it;
- how to appropriately use the RPE according to the producer’s instruction (it should be ensured that instructions for the workers are accessible and clearly written);
- that RPE is the last element securing a worker (after all other preventive measures have been taken) and therefore it is vital to use it throughout the entire time of exposure to a hazard;
- how to clean and when to withdraw the RPE from use;
- how to safely dispose of used RPE.
Trainings concerning RPE use ought to be organised at the employer’s expense and during working hours. Moreover, they should include new or changing types of hazards and be repeated periodically.
Maintenance of RPE
A RPE is basically designed for personal use. If circumstances arise requiring it to be used by more than one person, appropriate measures should be taken to ensure health or hygiene for the different users. The employer is obliged to ensure washing, maintenance, repair or decontaminating of the RPE free of charge. 
Effective maintenance of RPE is required in order to ensure that the equipment continues to provide the degree of protection for which it was designed. Maintenance includes cleaning, disinfection, examination, repair, testing, and safe storage. Maintenance details are usually provided by the manufacturer. The RPE should be examined before each use, with particular attention being paid to all rubber parts such as face pieces, exhalation valves, breathing tubes, and head harnesses. If the equipment is in a bad condition, it should not be used.
Reusable RPEs requires cleaning and disinfection after each use according to the procedures and means specified by the manufacturer.
The user of an RPE may carry out simple maintenance, such as replacing the filter(s), but more complicated repairs should only be undertaken by relevant personnel or services authorised by the manufacturer.
RPE should not be stored together with toxic substances or substances that may negatively influence materials from which it is produced, or such materials that give off unpleasant smells.
It is unacceptable that RPE and its elements be stored in places that may be directly exposed to sunlight or less than 1m from heating devices. RPE should be transported in conditions ensuring protection from damage and atmospheric influences. Time of storing should be no longer than the one specified by the producer as using expired or damaged filter or gas-filters, and also face pieces, may lead to poisoning. In case of reusable filters, it is necessary to secure it by placing RPE in an individual airtight container directly after leaving the contaminated area.
After each use, face pieces that are reusable ought to be washed in warm water with soap and then thoroughly dried by leaving them to dry in a non-contaminated area. It is recommended to carry out frequent disinfection of face pieces (according to the producer’s instruction) and after each change of user. During periodical RPE reviews and before and after each use, it is necessary to check the correct functioning of valves, and – if necessary – replace valves. Valves that are out-of-order and lack tightness may become the reason of very serious poisoning.
RPE protects the individual wearer against inhalation of hazardous substances and particles in the workplace air. RPE should be considered as a last resort and only be used after all other reasonably practicable control measures have been taken. Different types of RPE are available and the selection of the most suitable RPE for should be based on a risk assessment and take into account aspects such as the duration of the task and specific wearer requirements.
 Directive 89/656/EEC - use of personal protective equipment of 30 November 1989 on the minimum health and safety requirements for the use by workers of personal protective equipment at the workplace. Available at: 
 Regulation (EU) 2016/425 on personal protective equipment of the European Parliament and of the Council of 9 March 2016 on personal protective equipment and repealing Council Directive 89/686/EEC (with effect from 21 April 2018). Available at: 
 Regulation 2017/745/EU of the European Parliament and of the Council of 5 April 2017 on medical devices, amending Directive 2001/83/EC, Regulation (EC) No 178/2002 and Regulation (EC) No 1223/2009 and repealing Council Directives 90/385/EEC and 93/42/EEC. Available at: https://eur-lex.europa.eu/legal-content/EN/TXT/?qid=1588070668631&uri=CELEX:32017R0745
 EU Commission, PPE Regulation Guidelines - Guide to application of Regulation EU 2016/425 on personal protective equipment, 2018. Available at: 
 Commission communication in the framework of the implementation of Regulation (EU) 2016/425 of the European Parliament and of the Council on personal protective equipment and repealing Council Directive 89/686/EEC (Publication of titles and references of harmonised standards under Union harmonisation legislation) (2018/C 209/03). available at: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52018XC0615(03)
 HSE, Respiratory protective equipment at work, A practical guide, 2013. Available at: https://www.hse.gov.uk/pubns/books/hsg53.htm
 HSA, A Guide to Respiratory Protective Equipment. 2010. Available at: https://www.hsa.ie/eng/Publications_and_Forms/Publications/Chemical_and_Hazardous_Substances/Respiratory%20Protective%20Equipment.pdf
 EN 529 Respiratory protective devices - Recommendations for selection, use, care and maintenance (Guidance document)
 Zhuang Z., Landsittel D., Benson S., Roberge R., Shaffer R., Facial anthropometric differences among gender, ethnicity, and age groups, The Annals of Occupational Hygiene, 2010, 54(4), pp. 391-402.
 EN 167 Personal eye-protection. Optical test methods
EU-OSHA – European Agency for Safety and Health at Work, Risk assessment essentials. Available at: https://osha.europa.eu/en/publications/risk-assessment-essentials/view
EU-OSHA – European Agency for Safety and Health at Work, Risk assessment, the key to healthy workplaces, Factsheet. Available at: https://osha.europa.eu/en/publications/factsheet-81-risk-assessment-key-healthy-workplaces/view
EU Commission, Personal protective equipment, https://ec.europa.eu/growth/sectors/mechanical-engineering/personal-protective-equipment_en
ESF - European Safety Federation, https://eu-esf.org
HSE – Health and Safety Executive, Guidance on Regulations “Personal protective equipment at work (Third edition)", HSE Books, 2015. Available at:: http://www.hse.gov.uk/pubns/books/l25.htm
CCOHS – Canadian Centre for Occupational Health and Safety (2011_0106). Designing an Effective PPE Program. Retrieved on 30 January 2013, from: http://www.ccohs.ca/oshanswers/prevention/ppe/designin.html