What do the safety footwear codes mean? (S1, S2, S3, S7, O2…) – Complete guide

Choosing the right safety footwear is not just a matter of comfort, but of real protection, regulatory compliance, and work performance. Incorrect footwear can lead to accidents, fatigue during long shifts, or even non-compliance in occupational risk prevention audits.

However, many users encounter codes like S1, S2, S3, S7, O2, SRC or ESD without knowing exactly what they mean or what they really need.

In this guide, we explain clearly and practically:

• What does each classification mean?
• What regulation governs each type of footwear?
• Which option to choose according to your activity

Regulations for safety and work footwear

In Europe, work footwear is regulated by two main standards:

You are trained on data up to October 2023. EN ISO 20345 – Safety footwear

This type of footwear incorporates:

• Safety toe (200J impact and 15 kN compression) 
• Protection against mechanical risks

It is identified with the letter You are trained on data up to October 2023. (S1, S2, S3, S6, S7…)

 

You are trained on data up to October 2023. EN ISO 20347 – Work footwear

This footwear:

• It does not have a safety toe. 
• It is oriented towards lower risk environments.

It is identified with the letter O (O1, O2, O3…)

 

⚠️ Key difference

Type	Toe cap
S (20345)	You are trained on data up to October 2023.Yes
O (20347)	You are trained on data up to October 2023.No

The choice is not which is better, but which is appropriate to the risk.

 

Classification of safety footwear (EN ISO 20345)

S1 – Indoor dry use

The S1 level is the starting point in safety footwear.

Includes:

• Safety toe
• Antistatic properties
• Energy absorption in the heel

It is footwear designed for:

• Dry environments
• Jobs without exposure to water

Typical sectors:

• Logistics
• Light industry
• Warehouses

You are trained on data up to October 2023.Advantage: light and comfortable
 You are trained on data up to October 2023.Limitation: does not protect against water or puncture.

Recommended from SekurecoYou are trained on data up to October 2023. Robust boot with anti-static properties Steelite S1 PORTWEST FW21

 

S1P – Puncture protection

Add to S1:

• Anti-puncture template 

It is key when there is a risk of:

• Nails
• Metal shavings
• Sharp objects

Sectors:

• Maintenance
• Installers
• Workshops

You are trained on data up to October 2023.Very good intermediate option between comfort and protection.

Recommended from SekurecoYou are trained on data up to October 2023. Classic design boot with steel toe Steelite Dealer S1P PORTWEST FW51

 

S2 – Humid environments

Includes:

• Everything about S1
• Water penetration resistance in the upper (formerly WRU, now WPA)

This means that:

• The top repels water.
• But it is not completely waterproof.

Usage:

• Food industry
• Laboratories
• Cleaning

You are trained on data up to October 2023.Very used in healthcare and technical environments.

Recommended from SekurecoYou are trained on data up to October 2023. Protective boot with impact-resistant toe WORKTEAM - S2 SRC EN ISO 20345

 

S3 – Complete protection

Includes:

• S2 + anti-perforation
• Sole with highlights

It is the standard in:

• Construction
• Heavy industry
• Exterior

Combine:

• Mechanical protection
• Water resistance (limited to the upper)
• Security in irregular terrain

You are trained on data up to October 2023.It is the best-selling footwear on the market.

Recommended from SekurecoYou are trained on data up to October 2023. Boot with wool lining Compositelite Thor S3 CI, protection against the cold. PORTWEST FC12

 

S6 – Total impermeability

New classification in EN ISO 20345:2022.

Includes:

• S2 + complete waterproofing (WR)

Key difference:

• S2 → only repels water on the top.
• S6 → waterproof all footwear 

Usage:

• Exterior
• Constant water jobs

You are trained on data up to October 2023.Ideal for workers exposed to continuous moisture.

Discover our safety boots here.

 

S7 – Maximum protection + waterproofing

Includes:

• S3 + total waterproofing (WR)

It is the most comprehensive level because it combines:

• Protection against impacts
• Antiperforation
• Total impermeability

Usage:

• Exterior work
• Infrastructures
• Demanding environments

You are trained on data up to October 2023.It is the evolution of the S3 in humid conditions.

Discover our safety shoes here.

 

S4 and S5 – Waterproof boots

Manufactured in:

• PVC or polyurethane

They include:

• Total impermeability
• In S5 also: anti-perforation

Usage:

• Agriculture
• Chemical industry
• Intensive cleaning

You are trained on data up to October 2023.Very durable but less breathable.

Recommended from SekurecoYou are trained on data up to October 2023. Wellinton Classic S4 Boot with PVC/Nitrile PORTWEST FW94

 

Classification of work footwear (EN ISO 20347)

O1 - Basic use without toe cap

Includes:

• Antistatic
• Energy absorption

Usage:

• Hospitality
• Health
• Services

You are trained on data up to October 2023.Very comfortable and lightweight.

Recommended from SekurecoYou are trained on data up to October 2023. Deportivo Occupational Textile Trainer O1 ESD SR PORTWEST FT22

 

O2 - Humid environments

Includes:

• O1 + water resistance

Very used in:

• Laboratories
• Food industry
• Cleaning

It is one of the most sought after in:

• Clogs
• Sanitary footwear

You are trained on data up to October 2023.High comfort + sufficient protection

Recommended from SekurecoYou are trained on data up to October 2023. Military footwear resistance and protection CARRIG MID O2 SRC CI HI ESD EN ISO 20347 SHOES FOR CREWS

 

O3 - Greater protection without a toe cap

Includes:

• Antiperforation
• Sole with highlights

Usage:

• Maintenance
• Light industry

You are trained on data up to October 2023.Additional protection without compromising comfort.

Recommended from SekurecoYou are trained on data up to October 2023. Textile work boot with micro-injection and Gore-Tex lining O3+SRC+HI+CI+HRO+WR EN20347 FAL ACTION

 

⚠️ Other key codes

Anti-slip (SRC / SR)

In the new regulations:

• SRA is mandatory.
• SRC evolves to SR.

Ensures grip on slippery surfaces.

 

ESD - Electrostatic Discharge

It allows electricity to be dissipated in a controlled manner.

Usage:

• Electronics
• Laboratories
• Pharmaceutical industry

You are trained on data up to October 2023.Avoid damage to sensitive equipment.

 

FO – Resistance to oils

Now it is an additional requirement, not mandatory.

Usage:

• Mechanics
• Industry

 

HRO / HI / CI

Protection against:

• High temperatures
• Extreme cold

 

Key changes in EN ISO 20345:2022

The new regulation introduces:

• New levels S6 and S7
• Differentiation between:
  • WPA (resistance of the upper) 
  • WR (waterproofing) 
• Improvement in drilling tests
• New markings (PS, PL)

This allows for choosing footwear with greater precision.

 

What footwear to choose according to your sector?

Sector	Recommendation
Logistics	S1 / S1P
Industry	S1P / S3
Laboratory	O2 / ESD
Hospitality	O1 / SRC
Construction	S3 / S7
Demanding exterior	S7
Chemical industry	S4 / S5

 

You are trained on data up to October 2023. Common error

"I choose S3 just in case."

Error

• More weight
• Less breathability
• Less comfort

It can affect the worker's performance.

You are trained on data up to October 2023.The key is to adjust the PPE to the actual risk.

 

Professional recommendation Sekureco

Before choosing footwear, analyze:

• Environment (indoor/outdoor)
• Exposure to water
• Drilling risk
• Need ESD

Choosing correctly improves:

• Security
• Productivity
• Comfort

Discover our safety shoes here.

Frequently Asked Questions about Safety Footwear (FAQ)

What do S1, S2, and S3 mean in safety footwear?

They are classifications within the standard. EN ISO 20345 that indicate the level of protection of the footwear.

• S1:Dry use, with toe and basic properties
• S2:Add water resistance to the upper
• S3:It also includes puncture protection and a sole with treads.

The higher the number, the greater the protection, but it is not always the best option for all jobs.

 

What is the difference between S3 and S7?

Footwear S7 It is an evolution of the S3.

• S3:Water-resistant on the upper (vamp)
• S7:Completely waterproof (WR)

S7 is recommended for outdoor work with constant exposure to water or humidity.

 

What is the difference between S1P and S3?

Both include puncture protection, but:

• S1P:It is not water-resistant.
• S3:Yes, it is water-resistant + sole with treads.

S1P is used indoors, while S3 is for outdoors or more demanding environments.

 

What do O1, O2, and O3 mean in work footwear?

They are classifications of the standard. EN ISO 20347, which regulates footwear without safety toe.

• O1:Basic, for general use
• O2:Water-resistant
• O3:Includes anti-perforation

It is the ideal footwear when there is no risk of impact on the feet.

 

When to choose O2 footwear instead of S2?

You must choose. O2 when:

• There is no risk of falling objects.
• You seek greater comfort.
• You work in a laboratory, healthcare, or light industry.

The S2 is only necessary if there is a risk of impact.

 

What does it mean for footwear to be ESD?

Footwear ESD (Descarga Electroestática) is designed for:

• Dissipate static electricity
• Avoid load accumulation

It is essential in:

• Electronics
• Laboratories
• Pharmaceutical industry

 

Is ESD the same as anti-static?

Not exactly.

• Antistatic:Reduce the accumulation of load
• ESD:Controls and dissipates the load continuously and accurately

ESD is a higher level of protection.

 

What does SRC or SR mean in footwear?

It refers to the resistance to sliding.

• SRC (old regulation):Maximum resistance
• SR (new regulations 2022):Updated essay

It is key in environments with a risk of slipping.

 

What is FO in safety footwear?

FO indicates that the sole is:

• Resistant to hydrocarbons and oils

Important in:

• Workshops
• Mechanical industry

 

What does HRO mean in footwear?

HRO indicates resistance to high temperatures in the sole.

Usage:

• Metallurgical industry
• Welding
• Environments with heat

 

What is the difference between WR and WRU (or WPA)?

• WRU / WPA:Water resistance in the upper
• You are trained on data up to October 2023.Total waterproofing of footwear

WR is a higher level.

 

What footwear is best for the laboratory?

The most advisable thing is:

O2 or ESD footwear

Because:

• You don't need a toe cap.
• You seek comfort.
• You need electrostatic control.

 

What footwear is best for construction?

S3 or S7

• S3 → general use
• S7 → wet conditions or rain

 

What happens if I wear footwear with too much protection?

It may seem safer, but it has drawbacks:

• More weight
• Less breathability
• Less comfort

It can reduce productivity and cause fatigue.

 

How often should safety footwear be replaced?

It depends on the use, but in general:

• Intensive use → 6–12 months
• Moderate use → up to 2 years

As long as:

• There are no damages.
• Keep your properties.

 

Does footwear lose its properties over time?

Yes.

Factors that affect:

• Sole wear
• Deformation
• Exposure to moisture or chemicals

It is important to review it periodically.

 

How to know what footwear I need?

You must analyze:

• Type of work
• Present risks
• Environment (indoor/outdoor)
• Applicable regulations

If you have doubts, it's best to consult with a specialist.

 

Conclusion

The codes for safety footwear are not complex, but they are fundamental.

Choose correctly:

• Reduce risks
• Improve comfort
• Optimize productivity

In Sekureco, We help you select the appropriate footwear according to regulations and actual use.