Home / LEV Testing / Guide
LEV testing - preparation
An LEV examination goes better when the site is ready for it. None of the preparation is onerous, but a little of it makes the day smoother, quicker and more useful - the examiner can get to the system, see it working as it normally does, and draw on its history. Here is what to have ready so examination day runs well.
The short answer
Preparing for an LEV examination is mostly about three things. First, access: make sure the examiner can reach the whole system - the hoods, the ductwork and access points, the fan and the filters - without having to clear obstructions or wait for keys. Second, records: have the previous examination reports, the commissioning data and the logbook to hand, so the examiner knows the system's history and benchmark. Third, normal running: arrange for the processes to be operating as they usually do, because the system has to be tested under real working conditions. Get these ready and the examination is quicker, smoother and more useful.
Why preparation helps
An LEV examination will happen whether or not you prepare for it, but a little preparation makes a real difference to how it goes. An examiner arriving to a site that is ready can get straight to the work - reaching the system, seeing it run, drawing on its records - rather than spending time clearing access, hunting for paperwork or waiting for a process to be switched on. That makes the day quicker and less disruptive, and it makes the examination itself more thorough, because the examiner spends their time examining rather than dealing with avoidable obstacles.
None of the preparation is demanding - it is mostly about having things ready that you have anyway. But the payoff is worth the small effort: a test that is efficient, that captures the system working as it really does, and that benefits from the full picture of the system's history. Preparation is not about putting on a show for the examiner or hiding problems - the point of the examination is to find any problems - but about removing the friction that would otherwise slow the day and, worse, might mean the examination is done under conditions that do not reflect how the system normally works.
Access
The most practical piece of preparation is access. An examination looks at the whole system - the hoods at each process, the ductwork and its access points, the fan, and the filters - so the examiner needs to be able to reach all of it. That means making sure nothing is blocking access: stock piled in front of a duct run, a fan in a plant room that is locked, an access panel obstructed by equipment. Clearing the way in advance means the examiner can get to every part of the system rather than having to work around obstructions or leave a section unexamined because it could not be reached.
Access also covers the practical logistics: keys to any locked areas the system passes through, safe means of reaching parts at height if the layout requires it, and someone available who knows the site and can point out where the system runs. A system that snakes through several areas of a building is much easier to examine when someone can guide the examiner to each part and unlock what needs unlocking. Sorting this out before the day, rather than discovering a locked plant room mid-examination, keeps the process moving and ensures the whole system actually gets examined rather than just the accessible parts.
Records
The second piece of preparation is having the system's records ready. An examination is far more informative when the examiner can see the system's history: the previous examination reports, which show how the system performed before and what was found; the commissioning data, which gives the benchmark performance the system achieved when new; and the logbook, which records the checks, maintenance and faults since the last examination. Together these let the examiner compare the system's current state against its past and its benchmark, rather than assessing it in isolation.
This matters because judging a system is partly about change over time. A capture velocity reading means much more when it can be compared against the commissioning benchmark and the last examination - is it holding, or has it dropped? A recurring fault noted in the logbook may explain a reading that would otherwise be puzzling. So having the records to hand is not a paperwork formality; it genuinely improves the examination, letting the examiner interpret what they measure in the light of the system's history. Gathering the reports, commissioning data and logbook before the day means the examiner has the full picture from the start.
Normal running conditions
The third piece is arranging for the system to be tested under normal running conditions. An LEV has to be examined while it is doing its job - the processes it serves operating as they usually do, the system running as it normally runs - because the point is to confirm it controls exposure in real use, not in some artificial idle state. So preparing means ensuring the relevant processes will be running on examination day, and running as they typically do, so the examiner sees the system working under the conditions it actually faces.
This can take a little coordination: making sure the processes are scheduled to run when the examiner is there, that the system is in its normal operating configuration, and that nothing unusual is happening that would make the day unrepresentative. It is worth getting right, because a system examined under abnormal conditions - processes off, the system idling, an atypical setup - gives a misleading picture. The examiner needs to see the real thing. A brief conversation in advance about what needs to be running, and when, ensures the examination captures the system as it genuinely operates, which is the only way the result is meaningful. Preparing the running conditions is preparing for a test that actually tells you something.
The takeaway
A little preparation makes an LEV examination smoother, quicker and more useful, and it comes down to three things. Access: clear the way to the whole system - hoods, ductwork, access points, fan and filters - with keys for locked areas and someone to guide the examiner, so every part actually gets examined. Records: have the previous reports, commissioning data and logbook to hand, so the examiner can interpret current readings against the system's history and benchmark. Normal running: arrange for the processes to be operating as they usually do, so the system is tested under real conditions.
None of this is onerous, and none of it is about hiding problems - the examination exists to find them. It is about removing the friction that would slow the day and ensuring the test reflects how the system really works. A site that is ready lets the examiner spend their time examining, captures the system in genuine operation, and draws on its full history - which makes for an examination that is both efficient and genuinely informative. A small amount of preparation, a noticeably better result.
Questions
Mostly three things: access, so the examiner can reach the whole system; records, so they can see its history and benchmark; and normal running conditions, so the system is tested as it really works. None is onerous, but together they make the day quicker, smoother and more useful.
To the whole system - the hoods at each process, the ductwork and its access points, the fan and the filters. That means clearing obstructions, having keys for locked areas like plant rooms, safe means to reach parts at height, and ideally someone who knows the site to guide them.
The previous examination reports, the commissioning data that gives the system's benchmark performance when new, and the logbook of checks, maintenance and faults since the last examination. Together they let the examiner interpret current readings against the system's history rather than in isolation.
Because an LEV has to be tested while it is doing its job - the system controls exposure in real use, so it must be examined under normal running conditions. A system examined idle or with processes off gives a misleading picture; the examiner needs to see it working as it genuinely does.
No - the examination exists to find any problems, so hiding them would defeat the point. Preparation is about removing friction that would slow the day and ensuring the test reflects how the system really works, so the examiner spends their time examining rather than dealing with avoidable obstacles.
Yes. A ready site lets the examiner get straight to the work, reach every part of the system, see it running as it should, and draw on its full history to interpret the results. That makes the examination both more efficient and more informative than one done around obstructions and missing records.
We tell you exactly what to have ready for examination day - access, records and running conditions - so the thorough examination is efficient, representative and draws on your system's full history.
