From what pressure does the PED apply?

Article 1(1) of Directive 2014/68/EU applies it to pressure equipment and assemblies with a maximum allowable pressure PS greater than 0.5 bar. That is only the outer boundary. Whether an item needs CE marking depends on the Article 4(1) thresholds: a vessel for a Group 2 gas, for example, enters the categories only above 1 litre and a PS·V of 50 bar·L. Below the thresholds, equipment above 0.5 bar is designed to sound engineering practice under Article 4(3) and must not bear the CE marking under the PED.

Does a liquid-cooling loop in electronic equipment fall under the PED?

Usually not into a category. A water-based coolant is normally a Group 2 liquid, and Article 4(1)(a)(ii) only brings a Group 2 liquid vessel into the categories when PS exceeds 10 bar and PS·V exceeds 10 000 bar·L, or when PS exceeds 1 000 bar. Group 2 liquid piping enters only above 10 bar, DN 200 and a PS·DN of 5 000 bar. A loop above 0.5 bar but below those limits is designed to sound engineering practice and carries no PED CE marking. The fluid group must still be checked: under Article 13, a fluid becomes Group 1 if the maximum allowable temperature exceeds its flashpoint.

Is pressure equipment inside a machine or a low-voltage product excluded?

Partly. Article 1(2)(f) excludes equipment classified no higher than category I that is covered by the Machinery Directive, the Lifts Directive, the Low Voltage Directive, the Medical Devices Directive, the Gas Appliances Directive or the ATEX Directive. Pressure equipment of category II and above inside such a product stays under the PED. Separately, Article 1(2)(l) excludes enclosures for high-voltage electrical equipment such as switchgear, control gear, transformers and rotating machines.

What makes a fluid Group 1 under the PED?

Article 13 defines Group 1 by reference to the CLP Regulation: unstable explosives and explosives of divisions 1.1 to 1.5, flammable gases of category 1 and 2, oxidising gases of category 1, flammable liquids of category 1 and 2 (and category 3 when the maximum allowable temperature is above the flashpoint), and several other physical and health hazard classes, including acute inhalation toxicity of category 1 to 3. Group 1 also includes any fluid held at a maximum allowable temperature above its flashpoint. Everything else is Group 2.

Which conformity modules apply per PED category?

Article 14(2) sets them. Category I: module A. Category II: A2, D1 or E1. Category III: B (design type) + D, B (design type) + F, B (production type) + E, B (production type) + C2, or H. Category IV: B (production type) + D, B (production type) + F, G, or H1. The manufacturer may also choose a procedure from a higher category.

Are safety accessories always category IV?

As a rule, yes: point 2 of Annex II classifies safety accessories in category IV. But Annex II makes an exception: safety accessories manufactured for specific equipment may be classified in the same category as the equipment they protect. Pressure accessories such as valves are different again: they are classified on their own PS, their volume or nominal size, and the fluid group, using the vessel or piping tables.

What hydrostatic test pressure does the PED require?

For pressure vessels, point 7.4 of Annex I sets the hydrostatic test pressure at no less than the greater of two values: 1.25 times the maximum loading in service, taking account of PS and the maximum allowable temperature, or 1.43 times PS. Where a hydrostatic test is harmful or impractical, point 3.2.2 allows other tests of recognised value, preceded by additional measures such as non-destructive tests.

What is the difference between the PED and the Simple Pressure Vessels Directive?

Directive 2014/29/EU covers series-produced welded vessels for air or nitrogen, not fired, made of non-alloy quality steel, non-alloy aluminium or non-age-hardening aluminium alloys, with PS up to 30 bar and PS·V up to 10 000 bar·L, and working temperatures between -50 °C and 300 °C for steel or 100 °C for aluminium. Article 1(2)(c) of the PED excludes those vessels. Anything outside that envelope, a stainless steel vessel or a vessel for another gas for instance, is assessed under the PED.

PED 2014/68/EU: thresholds, categories I-IV, modules

Hugues Orgitello updated 6 Oct 2026 11 min read

Directive 2014/68/EU, the Pressure Equipment Directive (PED), applies to pressure equipment and assemblies with a maximum allowable pressure PS above 0.5 bar. That sentence is where most summaries stop, and it is the least useful part of the text. Whether an item needs a notified body, a CE marking, or only sound engineering practice is decided by the numeric thresholds of Article 4, the fluid groups of Article 13 and the tables of Annex II. This guide gives those numbers as the directive states them, lists the 21 exclusions of Article 1, and answers the question electronics teams actually ask: does a liquid-cooling loop need the PED?

In short:

0.5 bar is the outer boundary, not the trigger. CE marking starts at the Article 4(1) thresholds, for example above 1 litre and 50 bar·L for a vessel holding a Group 2 gas such as compressed air.
Below the thresholds, equipment above 0.5 bar follows sound engineering practice under Article 4(3), with instructions for use and no PED CE marking.
Article 1(2) lists 21 exclusions, among them equipment of category I or lower that is covered by the Low Voltage, Machinery, ATEX and three other directives, and enclosures for high-voltage switchgear.
A water-based cooling loop rarely reaches a category: Group 2 liquid vessels only enter above 10 bar and 10 000 bar·L.
Safety accessories are category IV, unless they are made for specific equipment, in which case they can take that equipment's category.

The entry thresholds of Article 4(1)

Every item of pressure equipment above 0.5 bar is in the directive's scope, but only those above the following limits must meet the essential safety requirements of Annex I and go through a category. The distinction between a gas and a liquid is the vapour pressure at the maximum allowable temperature: more than 0.5 bar above normal atmospheric pressure (1 013 mbar) means the gas column.

Equipment	Fluid	Enters the categories when	Annex II table
Vessel	Group 1 gas	V > 1 L and PS·V > 25 bar·L, or PS > 200 bar	Table 1
Vessel	Group 2 gas	V > 1 L and PS·V > 50 bar·L, or PS > 1 000 bar; all portable extinguishers and breathing apparatus bottles	Table 2
Vessel	Group 1 liquid	V > 1 L and PS·V > 200 bar·L, or PS > 500 bar	Table 3
Vessel	Group 2 liquid	PS > 10 bar and PS·V > 10 000 bar·L, or PS > 1 000 bar	Table 4
Fired or heated equipment with risk of overheating, for steam or superheated water above 110 °C	Any	V > 2 L; all pressure cookers	Table 5
Piping	Group 1 gas	DN > 25	Table 6
Piping	Group 2 gas	DN > 32 and PS·DN > 1 000 bar	Table 7
Piping	Group 1 liquid	DN > 25 and PS·DN > 2 000 bar	Table 8
Piping	Group 2 liquid	PS > 10 bar, DN > 200 and PS·DN > 5 000 bar	Table 9

Safety and pressure accessories intended for any of this equipment are covered too (Article 4(1)(d)), as are assemblies under the conditions of Article 4(2).

Below these limits, Article 4(3) applies: the equipment is designed and manufactured to the sound engineering practice of a Member State, comes with adequate instructions for use, and does not bear the CE marking under the PED. It may still carry a CE marking required by another act, such as the Low Voltage Directive.

Group 1 or Group 2: the fluid decides

Article 13 classifies fluids by reference to the CLP Regulation (EC) No 1272/2008. Group 1 covers substances and mixtures classified in these hazard classes:

unstable explosives, and explosives of divisions 1.1 to 1.5;
flammable gases, category 1 and 2; oxidising gases, category 1;
flammable liquids, category 1 and 2, and category 3 where the maximum allowable temperature is above the flashpoint;
flammable solids, category 1 and 2; self-reactive substances, types A to F; organic peroxides, types A to F;
pyrophoric liquids and solids, category 1; substances emitting flammable gases in contact with water, category 1 to 3;
oxidising liquids and solids, category 1 to 3;
acute oral and dermal toxicity, category 1 and 2; acute inhalation toxicity, category 1 to 3; specific target organ toxicity after single exposure, category 1.

Group 1 also includes any fluid held in equipment whose maximum allowable temperature exceeds the fluid's flashpoint. Group 2 is everything else: air, nitrogen, water, most inert gases.

Two rules follow from Article 13(2). A vessel with several chambers takes the highest category of its chambers. A chamber with several fluids is classified on the fluid that gives the highest category. And Annex II adds an exception for unstable gases: a vessel or piping that would fall in category I or II on tables 1 or 6 goes to category III.

Liquid cooling, refrigerants and enclosures: the PED in electronic equipment

For a site whose readers mostly build electronics, the PED questions tend to come from three places.

Liquid-cooling loops. A water or water-based coolant loop is usually a Group 2 liquid. Under Article 4(1)(a)(ii), a Group 2 liquid vessel enters the categories only when PS exceeds 10 bar and PS·V exceeds 10 000 bar·L, or PS exceeds 1 000 bar; Group 2 liquid piping only above 10 bar, DN 200 and a PS·DN of 5 000 bar. A server or power-electronics loop running at a few bar sits below these limits. If its PS is above 0.5 bar, it is designed to sound engineering practice, ships with instructions, and carries no PED CE marking. Two checks remain: whether the maximum allowable temperature exceeds the coolant's flashpoint, which would move it to Group 1, and whether an expansion tank or accumulator holds a gas cushion, which is assessed as a gas vessel.

Equipment already under another directive. Article 1(2)(f) excludes equipment classified no higher than category I that is covered by the Machinery Directive 2006/42/EC, the Lifts Directive 2014/33/EU, the Low Voltage Directive 2014/35/EU, the Medical Devices Directive 93/42/EEC, the Gas Appliances Directive 2009/142/EC or the ATEX Directive 2014/34/EU. A category I vessel in a low-voltage product is therefore handled under the LVD. A category II or higher vessel in the same product stays under the PED.

High-voltage enclosures. Article 1(2)(l) excludes enclosures for high-voltage electrical equipment such as switchgear, control gear, transformers and rotating machines, and Article 1(2)(m) excludes pressurised pipes containing transmission systems such as power and telephone cables.

Refrigerant circuits. A flammable refrigerant is a flammable gas under CLP, so a circuit holding one is classified on the Group 1 gas tables, which enter the categories at 25 bar·L for vessels and DN 25 for piping.

The 21 exclusions of Article 1(2)

The list is closed. The directive does not apply to:

Point	Excluded
(a)	Pipelines conveying fluids to or from an installation, from the last isolation device in the installation, except standard equipment in pressure reduction or compression stations
(b)	Water supply, distribution and discharge networks, and hydroelectric penstocks, pressure tunnels and shafts
(c)	Simple pressure vessels covered by Directive 2014/29/EU
(d)	Aerosol dispensers covered by Directive 75/324/EEC
(e)	Equipment for the functioning of vehicles under Directive 2007/46/EC and Regulations (EU) No 167/2013 and 168/2013
(f)	Equipment of category I or lower covered by the Machinery, Lifts, Low Voltage, Medical Devices, Gas Appliances or ATEX directives
(g)	Equipment covered by Article 346(1)(b) TFEU (military)
(h)	Items specifically designed for nuclear use whose failure may release radioactivity
(i)	Well-control equipment for petroleum, gas or geothermal extraction and underground storage
(j)	Casings or machinery where pressure is not a significant design factor, such as engines, turbines, compressors and pumps
(k)	Blast furnaces and associated metallurgical equipment
(l)	Enclosures for high-voltage electrical equipment
(m)	Pressurised pipes containing transmission systems such as power and telephone cables
(n)	Ships, rockets, aircraft and mobile offshore units, and equipment specifically for installation on board or their propulsion
(o)	Flexible-casing equipment such as tyres, air cushions, play balls and inflatable craft
(p)	Exhaust and inlet silencers
(q)	Bottles or cans for carbonated drinks for final consumption
(r)	Drinks transport and distribution vessels with PS·V up to 500 bar·L and PS up to 7 bar
(s)	Equipment under the transport of dangerous goods and transportable pressure equipment directives, the IMDG Code and the Chicago Convention
(t)	Radiators and pipes in warm water heating systems
(u)	Vessels for liquids with a gas pressure above the liquid of no more than 0.5 bar

Categories, modules and notified bodies

Within each Annex II table, demarcation lines set the upper limit of each category, from I to IV. Article 14(2) then gives the conformity assessment procedures available in each category; Annex III describes them, and the manufacturer may always choose a procedure from a higher category.

Category	Procedures (Article 14(2))
I	Module A, internal production control
II	A2, D1 or E1
III	B (design type) + D, B (design type) + F, B (production type) + E, B (production type) + C2, or H
IV	B (production type) + D, B (production type) + F, G, or H1

Two provisions of Article 14 are easy to miss. Under quality-assurance modules for category III and IV vessels and fired equipment, the notified body carries out unannounced visits, takes samples for the final assessment, and makes at least two visits in the first year of manufacturing (Article 14(4)). And an assembly is assessed globally (Article 14(6)): each component not already CE-marked, then the integration, then the protection against exceeding operating limits, each against the category that applies.

Accessories

Annex II gives three rules that are often merged into one:

Safety accessories, such as relief valves and bursting discs, are classified in category IV. By exception, safety accessories manufactured for specific equipment may take the category of the equipment they protect.
Pressure accessories, such as valves and fittings, are classified on their own PS, their volume or nominal size, and the fluid group, using the vessel or piping tables. Where both volume and nominal size are relevant, the higher category applies.
Specific items go up: portable extinguishers and breathing apparatus bottles are at least category III, and the design of pressure cookers needs a procedure equivalent to a category III module.

Testing, joints and personnel

Annex I sets the requirements that a notified body will look for in categories II to IV.

Requirement	Annex I point	What it says
Permanent joints	3.1.2	Joining by qualified personnel with suitable procedures; for categories II, III and IV, procedures and personnel approved by a notified body or a third-party organisation recognised by a Member State
Non-destructive testing	3.1.3	Qualified personnel; for categories III and IV, approved by a third-party organisation recognised by a Member State
Traceability	3.1.5	Material of pressure-bearing components identified from receipt to final test
Proof test	3.2.2 and 7.4	Hydrostatic test pressure no less than the greater of 1.25 × the maximum service loading (accounting for PS and maximum allowable temperature) and 1.43 × PS; other tests of recognised value where a hydrostatic test is harmful or impractical
Steel ductility	7.5	Elongation after rupture at least 14 % and impact energy on an ISO V test piece at least 27 J
Marking	3.3	Year of manufacture, identification, essential maximum and minimum allowable limits, plus the CE marking and notified body number where a body is involved in production control

Personnel approval for joints and NDT is a frequent audit finding: a welder qualification certificate is not the same thing as an approval by a recognised third party, and for categories III and IV the directive requires the latter.

Harmonised standards

Presumption of conformity comes from harmonised standards whose references are published in the Official Journal. The main families used under the PED are EN 13445 for unfired pressure vessels, EN 13480 for industrial metallic piping, EN 12952 for water-tube boilers, EN 12953 for shell boilers and EN ISO 4126 for safety devices against excessive pressure. Presumption attaches to the specific edition cited, so check the Commission's current list for the PED before relying on a standard.

PED or Simple Pressure Vessels Directive?

Article 1(2)(c) excludes from the PED the vessels covered by Directive 2014/29/EU. The envelope of that directive, from its Article 1, is narrow:

Criterion	Simple Pressure Vessels Directive 2014/29/EU
Production	Manufactured in series
Construction	Welded; a cylinder closed by dished or flat ends, or two dished ends
Fluid	Air or nitrogen, not fired
Material	Non-alloy quality steel, non-alloy aluminium or non-age-hardening aluminium alloys
Pressure	Internal gauge pressure above 0.5 bar, maximum working pressure up to 30 bar
PS·V	Up to 10 000 bar·L
Temperature	Minimum no lower than -50 °C; maximum no higher than 300 °C for steel and 100 °C for aluminium

Within it, Article 4 applies the essential requirements only above 50 bar·L; at 50 bar·L or less, vessels follow sound engineering practice. Above 50 bar·L, Article 13 requires an EU-type examination (module B), then module C1 above 3 000 bar·L, C1 or C2 between 200 and 3 000 bar·L, and C1 or C between 50 and 200 bar·L.

A stainless steel receiver, a vessel for CO2, or a vessel that is not series-produced falls outside that envelope and is assessed under the PED.

Timeline

Date	Event
29 May 2002	End of the period during which equipment complying with pre-existing national rules could be placed on the market (Article 48(1))
1 June 2015	Article 13 fluid classification, aligned on CLP, applies
19 July 2016	Directive 2014/68/EU applies in full and Directive 97/23/EC is repealed

Certificates and decisions issued under Directive 97/23/EC remain valid under the current directive (Article 48(3)).

Common mistakes

Mistake	What the text says
Treating 0.5 bar as the CE marking threshold	CE marking starts at the Article 4(1) thresholds; below them, sound engineering practice and no PED CE marking
Applying the PED to a category I vessel inside a low-voltage or machinery product	Article 1(2)(f) excludes it; the other directive applies
Assuming a pressure accessory inherits the vessel's category	Annex II point 3 classifies it on its own PS, size and fluid group
Treating every safety accessory as category IV	True by default, but Annex II point 2 allows the protected equipment's category for accessories made for specific equipment
Using the gas table for a liquid, or the reverse	The criterion is vapour pressure above 0.5 bar at the maximum allowable temperature
Ignoring the flashpoint rule	A fluid above its flashpoint at the maximum allowable temperature is Group 1
Assuming a welder certificate meets 3.1.3	For categories III and IV, NDT personnel need approval by a recognised third party

Frequently asked questions

From what pressure does the PED apply?: Article 1(1) of Directive 2014/68/EU applies it to pressure equipment and assemblies with a maximum allowable pressure PS greater than 0.5 bar. That is only the outer boundary. Whether an item needs CE marking depends on the Article 4(1) thresholds: a vessel for a Group 2 gas, for example, enters the categories only above 1 litre and a PS·V of 50 bar·L. Below the thresholds, equipment above 0.5 bar is designed to sound engineering practice under Article 4(3) and must not bear the CE marking under the PED.
Does a liquid-cooling loop in electronic equipment fall under the PED?: Usually not into a category. A water-based coolant is normally a Group 2 liquid, and Article 4(1)(a)(ii) only brings a Group 2 liquid vessel into the categories when PS exceeds 10 bar and PS·V exceeds 10 000 bar·L, or when PS exceeds 1 000 bar. Group 2 liquid piping enters only above 10 bar, DN 200 and a PS·DN of 5 000 bar. A loop above 0.5 bar but below those limits is designed to sound engineering practice and carries no PED CE marking. The fluid group must still be checked: under Article 13, a fluid becomes Group 1 if the maximum allowable temperature exceeds its flashpoint.
Is pressure equipment inside a machine or a low-voltage product excluded?: Partly. Article 1(2)(f) excludes equipment classified no higher than category I that is covered by the Machinery Directive, the Lifts Directive, the Low Voltage Directive, the Medical Devices Directive, the Gas Appliances Directive or the ATEX Directive. Pressure equipment of category II and above inside such a product stays under the PED. Separately, Article 1(2)(l) excludes enclosures for high-voltage electrical equipment such as switchgear, control gear, transformers and rotating machines.
What makes a fluid Group 1 under the PED?: Article 13 defines Group 1 by reference to the CLP Regulation: unstable explosives and explosives of divisions 1.1 to 1.5, flammable gases of category 1 and 2, oxidising gases of category 1, flammable liquids of category 1 and 2 (and category 3 when the maximum allowable temperature is above the flashpoint), and several other physical and health hazard classes, including acute inhalation toxicity of category 1 to 3. Group 1 also includes any fluid held at a maximum allowable temperature above its flashpoint. Everything else is Group 2.
Which conformity modules apply per PED category?: Article 14(2) sets them. Category I: module A. Category II: A2, D1 or E1. Category III: B (design type) + D, B (design type) + F, B (production type) + E, B (production type) + C2, or H. Category IV: B (production type) + D, B (production type) + F, G, or H1. The manufacturer may also choose a procedure from a higher category.
Are safety accessories always category IV?: As a rule, yes: point 2 of Annex II classifies safety accessories in category IV. But Annex II makes an exception: safety accessories manufactured for specific equipment may be classified in the same category as the equipment they protect. Pressure accessories such as valves are different again: they are classified on their own PS, their volume or nominal size, and the fluid group, using the vessel or piping tables.
What hydrostatic test pressure does the PED require?: For pressure vessels, point 7.4 of Annex I sets the hydrostatic test pressure at no less than the greater of two values: 1.25 times the maximum loading in service, taking account of PS and the maximum allowable temperature, or 1.43 times PS. Where a hydrostatic test is harmful or impractical, point 3.2.2 allows other tests of recognised value, preceded by additional measures such as non-destructive tests.
What is the difference between the PED and the Simple Pressure Vessels Directive?: Directive 2014/29/EU covers series-produced welded vessels for air or nitrogen, not fired, made of non-alloy quality steel, non-alloy aluminium or non-age-hardening aluminium alloys, with PS up to 30 bar and PS·V up to 10 000 bar·L, and working temperatures between -50 °C and 300 °C for steel or 100 °C for aluminium. Article 1(2)(c) of the PED excludes those vessels. Anything outside that envelope, a stainless steel vessel or a vessel for another gas for instance, is assessed under the PED.