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Safety Code of Practice for Carbon Dioxide Refrigerant (R744/CO2)

IOR report carbon front

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Safety Code of Practice for Carbon Dioxide Refrigerant (R744/CO2)

This IOR Code provides essential industry guidance for owners, designers, installers and operators of vapour compression refrigerating systems that use carbon dioxide as a refrigerant. It covers properties of refrigerants, decommissioning, testing and maintenance as well as design issues with useful appendices such as typical schedules for inspection and maintenance, system register details, machinery rooms, definitions and an updated list of relevant standards.  The Code has been prepared by the IOR Technical Committee as a reference source and guide to interpretation of current safety standards such as BS EN378:2016 and legal requirements such as PED, PSSR and PUWER.  

The IOR publishes four Safety Codes of Practice specific to refrigerant type.  

  • Non Flammable, Lower Toxicity Refrigerants Group A1 
  • Flammable Lower Toxicity Refrigerants Group A2L, A2 and A3 
  • Carbon Dioxide R744
  • Ammonia R717 

This Code is supplied as a 93 page PDF.


May 2019 - Addendum new Section 11 added - CLP and DSEAR

Aug 2019 - addition of footnote to Table 2, and minor text amendment to Annex F, section 4.1

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Full Contents list

Section 1 – Scope and Limitations            

Section 2 – Relevant Properties of Carbon Dioxide          

2.1 Carbon Dioxide         

2.2 Potential Hazards     


Section 3 – Design of Components          

3.1 General        

3.2 Component Design and Test Pressures          

3.3 Compressors             

3.3.1 General    

3.3.2 Design Criteria       

3.3.3 Pressure Testing   

3.3.4 Nameplate Data   

3.4 Pressure Vessels and Heat Exchangers          

3.4.1 General    

3.4.2 Design Pressures  

3.4.3 Test Pressures       

3.4.4 Nameplate Data   

3.4.5 Pressure Vessels  

3.4.6 Shell and Tube Heat Exchangers    

3.4.7 Coil or Grid Exchangers      

3.4.8 Plate and Plate & Shell Heat Exchangers    

3.5 Liquid Refrigerant Pumps     

3.5.1 Design Criteria       

3.5.2 Test Pressures       

3.5.3 Nameplate Data   

3.6 Refrigerant Control Valves and Sensing Devices         

3.6.1 General    

3.6.2. Design Pressure and Temperature              

3.6.3. Manufacturing Tests         

3.6.4 Nameplate Data   

3.6.5 Shut-Off Valves    

3.6.6 Liquid level indication         


Section 4 – System Design and Installation

4.1 General        

4.2 Material Selection   

4.3 Steel Piping Systems              

4.3.1 Pipe Materials       

4.3.2 Pipe Connections 

4.3.3 Pipe Supports and Hangers              

4.4 Copper Piping            

4.4.1 Pipe Connections 

4.4.2 Pipe Supports and Hangers              

4.5 Location and Arrangement of Piping

4.6 Arrangement of Isolating Valves       

4.7 Instrumentation       

4.7.1 General    

4.7.2 Arrangement of Pressure Indicators            

4.7.3 Liquid Level Indicators        

4.7.4 Liquid Level Glasses            

4.8 Protection against Excess Pressure  

4.9 Protection against Environmental Effects      

4.10 Notification to Local Authorities      

4.11 Refrigerant Detection          

4.12 System Labelling    

4.13  Allowable Refrigerant Charge         


Section 5 – System Testing         

5.1 General        

5.2 Strength Test Procedure      

5.3 Tightness Test Procedure     

5.4 Test Certificates       


Section 6 – Commissioning of New Installations

6.1 General        

6.2 Evacuation and Dehydration               

6.3 Charging      

6.4 Protection Devices  


Section 7 - Inspection and Maintenance               

7.1 General        

7.2 System Log 

7.3 Routine Inspection  

7.3.1 General    

7.3.2 Logging System Performance         

7.3.3 Pipework 

7.3.4 Compressors          

7.3.5 Condensers and Evaporators          

7.3.6 Liquid Pumps         

7.3.7 Pressure Relief Devices and Pressure Controls       

7.4 Major Inspection     

7.4.1 System     

7.4.2 Pipework

7.4.3 Compressors          

7.4.4 Pressure Vessels and Heat Exchangers       

7.4.5 Refrigerant Pumps              

7.4.6 Stop Valves, Safety Valves and Control Devices      

7.5 Pressure System Examination            

7.5.1 General    

7.5.2 Uninsulated Vessels and Heat Exchangers

7.5.3 Insulated Vessels and Heat Exchangers      

7.5.4 Extended Surface Heat Exchangers and Grid Coils 

7.5.5 Plate Heat Exchangers       

7.5.6 Piping        

7.5.7 Pressure Test for Strength               

7.5.8 Extent of Tightness Test    


Section 8 - Documentation         

8.1 General        

8.2 Risk Assessment      

8.3 Health and Safety File            

8.4 Written Scheme of Examination and Records              

8.5 Commissioning Records        

8.6 Refrigerant Inventory Record             

8.7 Contingency Provisions         

8.8 The System Register               

8.9 System Log 

8.10 Instruction Manuals             


Section 9 Decommissioning        

9.1  General       

9.2 Recovered Carbon Dioxide  

9.2.1 General    

9.2.2 Carbon dioxide Recovery  

9.2.3 Recovery for recycling to another system 

9.2.4 Recovery for disposal         


Section 10 – References, Standards and Legislation

Section 11 – Addendum: CLP and DSEAR         

APPENDIX A – Definition

APPENDIX B - Maximum Allowable Pressure and Strength Test Procedure           

APPENDIX C - Pneumatic Strength Pressure Test Procedure       

APPENDIX D – Marking and Name Plate Data     

APPENDIX E - Handling Transport and Storage of Refrigerant Cylinders  

APPENDIX F – Commissioning of New Installations          

APPENDIX G – Machinery Rooms and Auxiliary Safety Equipment            

APPENDIX H – Typical Schedule for Inspection and Maintenance              

APPENDIX I - Sample details for Register              

APPENDIX J - Sample Compressor Operating Data and System Log           

APPENDIX K – IOR Policy on Refrigerant Choice 

APPENDIX L – Sealed Freezers