Control measure

Dilution: Corrosive materials

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Control measure knowledge

This control measure should be read in conjunction with National Operational Guidance: Environmental Protection - Dilution

Dilution is a chemical method by which a water-soluble corrosive solution release is made larger but less corrosive by adding large volumes of water. This should be regarded as a last resort if no other method can be used. Specialist advice should be taken to ensure the corrosive can be safely and effectively diluted. Consultation with environment agencies and site operators must take place prior to any dilution.

These important criteria must be considered before dilution:

Concentration
pH
Water reactivity
Potential to generate heat and/or toxic vapours on contact with water
Potential to form any kind of solid or precipitate
Water solubility

As a general rule, dilution should only be attempted on liquid and solid corrosives, and only when all other reasonable methods of mitigation and removal have proven unacceptable.

In emergency situations, water sprays or 'curtains' may be used for controlling the spread of corrosive vapours to populated areas. This tactic will lead to a degree of 'scrubbing' of the vapour or gas cloud if the corrosive is water soluble. This means that the water run-off may itself become corrosive. This side effect may cause environmental damage unless it is controlled.

Dilution can be effective for small corrosive spills of up to one litre but environment agencies, water authorities and landowners should be consulted if the products of dilution are to be dispersed on-site.

The major disadvantage to dilution is that it is not well understood by emergency responders. It is not a straight, linear, one-to-one process. It is important to recognise that dilution is actually a logarithmic process (on a one-to-ten scale). The viability of the tactic will depend on the resulting pH that can be achieved.

Table 1: The resulting pH when diluting a one-litre spill of acid with increasing amounts of water
One-litre spill of acid with pH of 0
Water needed to dilute it 1 pH level	Resulting pH
10 litres	1
100 litres	2
1000 litres	3
10,000 litres	4
100,000 litres	5
1000,000 litres	6
10,000,000 litres	7 neutral

However, partial dilution to reduce the level of corrosivity and therefore reduce the hazard may be a suitable tactic in certain situations following specialist advice.

See National Operational Guidance: Environmental protection

Strategic actions

Fire and rescue services should:

Have procedures in place to enable responders to safely dilute corrosive materials
Ensure that responders understand the potential risks associated with dilution

Tactical actions

Incident commanders should:

Consider dilution and dispersal of corrosive materials as a last resort following consultation with relevant environmental agency
Confirm the suitability of the corrosive materials for dilution, in terms of physical and chemical properties
Consider using water sprays and 'curtains' to reduce and control corrosive vapours when they are threatening populated areas (but be aware that the run-off will be corrosive)

TRAINING SPECIFICATION

Knowledge and understanding

Control measure element	Learning outcome
Dilute corrosive materials	Understand: The process and potential hazards when diluting corrosive materials, as a last resort The criteria for consideration prior to dilution The general rule for dilution The potential environmental impact of diluting corrosive materials The limitations of diluting corrosive materials as a tactic Refer to – Dilution – Environmental training specification

Control measure element

Learning outcome

Dilute corrosive materials

Understand:

The process and potential hazards when diluting corrosive materials, as a last resort
The criteria for consideration prior to dilution
The general rule for dilution
The potential environmental impact of diluting corrosive materials
The limitations of diluting corrosive materials as a tactic

Refer to – Dilution – Environmental training specification

NOS knowledge and understanding

You need to know and understand:
You need to know and understand - TO BE ARCHIVED 2816
K The importance of maintaining the safety and welfare of yourself and others during fire and rescue incidents K Safe working practices of your organisation when responding to fire and rescue incidents K Hazards and risks of fire and rescue incidents affecting people, property and the environment K Your organisation's control measures to mitigate risk K Legislation, policies, procedures, guidelines and protocols that apply to your role K How to use available systems, tools, methods and templates to assist in the planning process K Relevant others you may work with and their role in and responsibilities K Resources available to respond to fire and rescue incidents K Suppression tactics and methods, their safe use and their impact on controlling fire and rescue incidents
Health and safety
K 1 The importance of maintaining the safety and welfare of yourself and others during fire and rescue incidents K 3 Safe working practices of your organisation when responding to fire and rescue incidents K 4 Hazards and risks of fire and rescue incidents affecting people, property and the environment K 7 Your organisation's control measures to mitigate risk
Organisational
K 9 Legislation, policies, procedures, guidelines and protocols that apply to your role K 10 How to use available systems, tools, methods and templates to assist in the planning process
Personal and interpersonal
K 12 Relevant others you may work with and their role in and responsibilities
Technical
K 20 Resources available to respond to fire and rescue incidents K 22 Suppression tactics and methods, their safe use and their impact on controlling fire and rescue incidents

Practical application

Control measure element	Learning outcome
Dilute corrosive materials	Demonstrate the ability to: Confirm the suitability of corrosive materials for dilution Apply safe and effective methods of dilution Refer to – Dilution – Environmental training specification

Control measure element

Learning outcome

Dilute corrosive materials

Demonstrate the ability to:

Confirm the suitability of corrosive materials for dilution
Apply safe and effective methods of dilution

Refer to – Dilution – Environmental training specification

NOS performance criteria

You must be able to:
Provide special advice to control fire and rescue incidents
P 1 Gather information for fire and rescue incidents within your area of expertise in line with your organisation's procedures P 2 Identify and maintain awareness of risk for fire and rescue incidents within your area of expertise in line with risk assessment processes P 3 Identify control measures to reduce fire and rescue risks in line with risk assessment processes P 4 Assess factors affecting fire and rescue incidents for your area of expertise and in line with the organisation's procedures P 5 Liaise with others to discuss the detail of what will be included in tactical plans, using information available, in line with your organisation's requirements P 8 Identify tactics which allow effective control methods in line with your organisation's requirements

You must be able to:

Provide special advice to control fire and rescue incidents

P 1

Gather information for fire and rescue incidents within your area of expertise in line with your organisation's procedures

P 2

Identify and maintain awareness of risk for fire and rescue incidents within your area of expertise in line with risk assessment processes

P 3

Identify control measures to reduce fire and rescue risks in line with risk assessment processes

P 4

Assess factors affecting fire and rescue incidents for your area of expertise and in line with the organisation's procedures

P 5

Liaise with others to discuss the detail of what will be included in tactical plans, using information available, in line with your organisation's requirements

P 8

Identify tactics which allow effective control methods in line with your organisation's requirements

Control measure
Treatment: Corrosive materials
Hazard
Biological agents not involved in fire

Hazardous Materials - Health Hazards

Control measure

Dilution: Corrosive materials

Control measure

Dilution: Corrosive materials

Control measure knowledge

Strategic actions

Tactical actions

TRAINING SPECIFICATION

Knowledge and understanding

NOS knowledge and understanding

You need to know and understand - TO BE ARCHIVED 2816

Practical application

NOS performance criteria