But labs also encompass point of care, phlebotomy, transfusion medicine, informatics, andrology, research, and logistics. Your role could vary from collecting and preparing specimens for testing, to performing the tests and reporting the results. Some roles focus on maintaining the lab equipment and supplies, or working on the software side, developing new tests for technicians to use.
You could also work in quality assurance and management. The size of the lab and the facility it's in can influence the range of roles available. Some facilities combine many roles, while others have separate staff for each task.
I've personally worked in a few labs measuring radioactivity. I started out in a commercial lab doing environmental radiochemical testing; then spent a few years at a company that set up a laboratory service for measuring radioactive waste; and am now working at a large international lab working on developing fusion energy.
To talk about what roles you can do in labs in general, perhaps it's worth remembering all labs are businesses or organisations of some kind, so some laboratory roles are all the usual business support roles - managers, HR, recruitment, finance, IT, safety, sales (usually business-to-business sales rather than to the public, but some labs do public advertising too). In larger organizations these might all be separate roles, and in smaller labs many of these responsibilities get combined with other roles.
Another important part of laboratory work is measurement quality. Many laboratories are accredited against standards like ISO/IEC 17025, so there's likely to be a quality team ensuring everything that supports the quality of measurements is done properly, like following procedures, maintaining environmental conditions, and keeping all records in order. In smaller labs, this is often a singular Quality Manager. My first job after graduating involved some quality work - I was crosschecking data and writing and checking the test reports.
Many labs deal with large numbers of different samples, so sample management is often a dedicated team or person. Some laboratories have people that go out and collect samples; others receive samples in from elsewhere, Sample receipt tasks involve recording Information about the sample like collection time and location, owner, sample conditions etc, and ensuring the sample is prepared for the right analysis. Preparation can involve things like physical or chemical processing (drying, homogenizing, acidification); taking subsamples for different kinds of analysis; ensuring proper containers and markings are used to prevent cross-contamination or any danger to lab staff; and organising storage until the analysts are ready to handle the sample.
Finally, the more technical roles of scientists and analysts. What exact roles involve depends on the type of lab - some of the other answers give some good examples in medical or chemical labs - but there's many more types of science and lab; I've met electronic engineers testing voltage, current, electromagnetic emissions, etc; mechanical engineers using crushing presses, tension tests, various electron microscopes looking at materials properties; and many more. I work in radiation measurement, setting up and using technologies like gamma and neutron spectrometry.
A particularly important difference in technical work comes out of the difference between analytical labs and research labs - with analytical labs, the science is well known, and the objective is just to analyse samples in a repetitive way and report on the properties of the samples. In research labs, you're looking to find out new science and discover new things, so the work is much less routine and much more exploratory science - that means there's much more academic research work for scientists, studying previous scientific papers, publishing new research, etc.
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