Rank: Forum user 
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I have recently tstarted a new job and they have unusual COSHH assessments. The assessments are made per lab activity, which typically consists of multple steps with upwards of 20 chemicals used through the activity. This has resulted in a single COSHH assessment with a significant amount of chemicals on one document. I don't believe the risks have been fully assessed, however, to redo these for the full buisness with 'common' process based assessments there would be easily over 1000 assessments. Do I work with them and update them as required or not?
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Rank: Super forum user
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There is nothing wrong with this approach. Task based assessments are acceptable. There maybe 20 chemicals in 1 assessment - however how hazardous are they? What quantity of each chemical is involved in each preparation? Are you suggesting, for example given here, to do 20 assessments for each lab preparation?? Sure you need to review each chemical to pick out any particular nasties and required safety precautions etc
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 1 user thanked Ian Bell2 for this useful post.
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I would go further than Ian and say all COSHH assessments should be task based! COSHH is about controlling exposure, and exposure comes from the activity. Also, without considering all the chemicals together in a task how can you look for interactions and intermedaries potentially produced! Substance based COSHH assessments are only truely effective if the substances are used on their own (with no other chemicals) and an assessment is done covering every task they are used for. You also tend to end up with a lot of 'if ... then' statements in the assessment, rather than 'do...' requirements. This may work for incidential use, but not in a lab.
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3 users thanked antbruce001 for this useful post.
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Rank: Super forum user
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I would agree COSHH assessments are nothing but task based assessments..so in this case you will have the incompatibility risks covered?...I am sure you do :) But that is where I would concentrate my effort what if the numbskull mixes the wrong material/ task step...
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2 users thanked stevedm for this useful post.
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Thank you, I have been trying to upload an example but its not working for some reason. I agree that they should be task based, however I don't feel that the risk is fully captured and the cost / time to change the system will be significant.
A bit more of an example to elaborate, a lab activity uses hexane, toluene, cyclohexane or DCM to exctract oil from water. Depending on the water type, either one of these is added to the water. It is then mixed with with a 50% hydrocholic solution that has been mixed with water. Acetone is then added and additional spiking and buffering chemicals that have been premixed. The current assessment lists all hazards (Properties, WEL, First aid, Fire, Spillage) for each BASE chemical used, and states the quantity used. Control measures are also stated. The piece I feel is missing is the hazard that is posed when mixing all of these chemicals and the document is already around 5 pages long. If an assessment was broken down into smaller steps, more accurate assessments could be made.
I hope this makes sense.
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Rank: Super forum user
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Hi Marc What do those at the front line think? May be they don't actually want one or more COSHH assessments, but rather a task based asssesment that covers all the various risks - including e.g. broken glass.
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Rank: Super forum user
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Task based every time and a five page document for a lab procedure is not unusual-my lab template starts at 8 pages. You need to capture all of the relevant information and what they intend to do with it.
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Rank: Super forum user 
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It's important to distinguish between these scenarios: 1. Essentially the same activity is undertaken, but separately using different chemicals that perform similar functions (eg they are all solvents, or all colour indicators) 2. A number of chemicals are mixed together In both cases, it is valid to have a risk assessment referring to multiple chemicals. But the risk assessment will look different. Scenario 1 has to tell you if there are any different precautions you have to take depending on whether you are using chemical A or chemical B. Scenario 2 has to tell you what happens when chemical A is mixed with chemical B. It's not clear to me which of these you are focused on. What you do not usually need is a risk assessment for chemical A and a separate risk assessment for chemical B. Although it's not what is usually needed, it is what is usually done, but don't be distracted by what is usually done because with COSHH assessment, what is usually done happens to be wrong.
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1 user thanked Kate for this useful post.
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Thanks Kate, that makes sense.
At the minute the assessments are a mix of both of your scenarios. If the worker deems it suitable they use chemical a, b or c, or possibly multiple then that is what they add. For example they add chemical a, run the test to get get a result then have to add more of a, or a combination of a, b or c.
Its not as simple as mixing two chemicals to get a new chemical, one assessment covers multiple stages to get to a final result, changing the hazards throughout.
Another example i have recently come across is mixing different acids to make aqua regia, a much stronger acid, but the coshh assessment only states the hazards for the initial two acids used. It is then boiled and further chemicals added, and I am preety sure this isnt covered, but im not 100% sure which way to go.
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Rank: Super forum user
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If there are stages in a sequence and the risks are different at each stage, then you do need to assess each stage. But you don't necessarily need a separate final document for each stage. There are all sorts of different ways you could split this up, based on what makes sense for you in doing the assessment and more importantly what makes sense for anyone who is expected to consult it. Is the risk assessment used as a communications tool or are the hazards and precautions communicated by other means?
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Hi Kate,
Thanks for the advise, i am now trying to plan a way to identify the risk at each stage of the tasks and communicate these.
At the minute the only way the risks are identified or communicated is through the assessments (there are technical instructions in place, but they do not contain any safety info, so not a safe system of work as i would expect). I am hoping to get the documented instructions to be updated to include the safety hazards and additional safety instructions from the COSHH assessments.
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Rank: Super forum user
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Hi Is this a lab scale process or pilot plant?
In the first case I would treat the whole thing including intermediaries as one process and focus on the really nasty stuff like the aqua regia. if you control that you will probably control the issues relating to the other components. I say probably so double check that is the case.
once you have moved to pilot plant then i would breakdown the process as the volumes involved become significant.
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Rank: Forum user
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@Kurdziel
The processes are all lab scale, small quantities but high concentrations, with a lot of mixing and compound changes.
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Rank: Super forum user
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A mistake a lot of people do in COSHH is to focus too much on the properties of the substances( which is essentially the hazard part of the risk assessment) and not on the process which is where the risk manifests itself. Look at the process in this case: how do you add the organic solvents to your water?- is it all poured in one go or added slowly etc? How do you mix it?-do they just invert the tub or do they vortex it? During mixing how is the tub sealed to prevent the mixture from leaking? Is the process taking place in a fume cupboard with sash down? are staff wearing suitable PPE? How do they prepare the HCl solution? And so it goes… Don't be scared of being thorough- risk assessment (despite what some people say) is not necessarily easy and straightforward. This a case of a cleaner diluting a product in a bucket.
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2 users thanked A Kurdziel for this useful post.
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Of course I should have said " This is NOT a case of a cleaner diluting a product in a bucket."
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1 user thanked A Kurdziel for this useful post.
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Originally Posted by: A Kurdziel  A mistake a lot of people do in COSHH is to focus too much on the properties of the substances( which is essentially the hazard part of the risk assessment) and not on the process which is where the risk manifests itself. Look at the process in this case: how do you add the organic solvents to your water?- is it all poured in one go or added slowly etc? How do you mix it?-do they just invert the tub or do they vortex it? During mixing how is the tub sealed to prevent the mixture from leaking? Is the process taking place in a fume cupboard with sash down? are staff wearing suitable PPE? How do they prepare the HCl solution? And so it goes… Don't be scared of being thorough- risk assessment (despite what some people say) is not necessarily easy and straightforward. This a case of a cleaner diluting a product in a bucket.
Thanks for this, I am steadily trying to make headway, one process at a time, and held a meeting with the top management to explain the complexities and actual time to carry out this for the full buisness. I have anticipated around 2-3 year project, they expected it done in less than a month or so.
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Rank: Super forum user
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Marc - of course management thought this would be easy! I hope that they have now accepted that doing it right will take some time.
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