Chemical Compatibility (Chemical Incompatibility) Assessment  

Do you understand the potential for adverse chemical reactions between substances at your site in your process or storage area? You may combine, blend, process, react, store or transport chemicals and there may be potential for different chemicals to come into contact with each other resulting in potential for harm and damage.  

 

If one chemical inadvertently mixes with another chemical, what could happen? Are the products from your process compatible? The chemical incompatibility of chemicals may be necessary to understand further in to support a HAZID or HAZOP and to input into COSHH assessments or DSEAR assessments. Often, questions arise at these workshops which can't be readily answered. So, why not have the answers ready in advance? 

 

We can perform a chemical reactivity assessment for binary pairs (X & Y) of substances and build-up a chemical compatibility (incompatibility) matrix for you using chemical reactivity databases. This can include a summary of the fire and explosion hazards, health hazards, firefighting techniques, cleanup procedures, protective clothing, and chemical properties. 

 

We can assess the chemical reactivity of thousands of common hazardous chemicals, advising on compatibility and suitability of materials of construction in chemical processes using reactivity databases. We can also summarise the chemical hazards in a comprehensive table including hazard statements, risk phrases, precautions, etc. We will also highlight special considerations and controls for design, operation, maintenance, handling, etc., for the hazardous chemicals. The chemical compatibility matrix provides a convenient way to visualise and communicate the risks so that effective controls on indvertent mixing of incompatible chemicals is avoided. It provides a greater level of detail and insight than simple charts do, such as that in HSG71 Chemical Warehousing by the UK HSE. 

 

Below is a snapshot of part of an example chemical compatibility matrix. Red cells show incompatible chemical combinations; yellow cells advise caution; and green cells show compatible chemical combinations; and black cells are N/A as it is the same chemical combination. Only X-Y (binary) chemical interactions can be assessed and not three or more chemical interactions.  

 

 

As identified in the DSEAR ACOP (L138), where substances are used together in a chemical process it will be necessary to carry out a chemical reaction hazard assessment to identify any adverse conditions that could give rise to hazardous heat and pressure effects. Where substances with different properties are processed together the fire properties of any resulting mixture will be different from the individual components. The properties of the mixture must be known to ensure, for example, any electrical equipment is suitable and any explosion relief provided is appropriate. Oxygen and other oxidising agents make most flammable substances easier to ignite, burn faster and become more difficult to extinguish. Many materials that are not classified as dangerous substances will become dangerous in the presence of an oxygen-enriched atmosphere or an oxidising agent. Where oxygen or other oxidising agents are used near to dangerous substances or combustible materials, the assessment must take into account the enhanced flammability properties.  

 

Consideration of the potential or known adverse physico-chemical interactions between different substances is an important part of DSEAR compliance.