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LEV testing - after a fail
A failed thorough examination and test is not the end of the story - it is the start of a decision. Repair the system, or replace it. Here is how to weigh the two honestly, rather than defaulting to the cheaper invoice.
The short answer
When an LEV test fails, the choice is repair or replace - and the right answer depends on more than the repair quote. A localised fault on a sound system is usually worth repairing; a system that is old, badly designed, undersized for the work it now does, or expensive to run is often cheaper to replace over its remaining life. The failed test is the moment to make that judgement deliberately rather than reaching for the cheapest fix.
First, understand the failure
A fail is not a single thing. A test can fail because a filter is spent, a fan has lost efficiency, a section of ductwork has come loose or a damper has stuck - discrete faults on a fundamentally sound system. Or it can fail because the system was never capable of controlling the exposure in the first place: hoods in the wrong place, capture velocity too low, ductwork undersized, or a system asked to do far more than it was designed for.
The report should make clear which of these you are dealing with. A discrete fault points towards repair; a fundamental design or capacity shortfall points towards replacement, because no amount of patching will make an inadequate system adequate. Reading the failure properly is the whole basis of the decision - which is another reason a thorough, well-documented examination is worth having.
The case for repair
If the underlying system is well designed and the failure is a specific, fixable fault, repair is usually the sensible route. Changing a loaded filter, replacing a worn fan, resealing or replacing a length of ductwork, or freeing a damper restores a capable system to working order at a fraction of replacement cost, and a re-test then confirms control is back.
Repair also wins where the system is relatively young and the fault is a maintenance lapse rather than a design flaw. In that case the failure is really a signal that the maintenance regime needs tightening - fix the fault, close the gap in upkeep, and the system has plenty of life left.
The case for replace
Replacement moves from sensible to necessary when the system is failing for structural reasons. A system whose hoods are poorly positioned, whose capture velocity is inadequate, or which is undersized for a process that has grown since it was installed will keep failing however many components you renew - because the fault is the design, not the parts. Money spent repairing it is spent keeping an inadequate control limping along.
Age and running cost tip the balance too. An old system that is inefficient to run, hard to get parts for, and repeatedly on the edge of failing can cost more over its remaining life - in energy, in repeated remedials, in re-tests - than a properly designed replacement. When repairs are becoming a pattern, the honest comparison is whole-life cost, not this one invoice.
The trap to avoid
The costly mistake is defaulting to repair every time because each individual fix looks cheaper than replacement. On a fundamentally inadequate system that produces a slow drip of remedial bills, re-tests and continued exposure risk, with the system never really controlling the hazard. Each repair is justified on its own, yet together they cost more than a replacement would have, and the underlying problem is never solved.
The failed test is the moment to step back and ask whether you are maintaining a capable system or subsidising an incapable one. If it is the latter, continuing to repair is the false economy, not the replacement.
Making the decision
The way through is to have the failure properly diagnosed first - not just what failed, but why - and then to cost both routes over the system's remaining life rather than on the day. A repair quote against a replacement quote, each set beside the expected running cost, re-test frequency and likelihood of further failures, turns an anxious either-or into a clear comparison.
Whichever way it goes, the aim is the same: a system that genuinely controls exposure and will pass its next thorough examination and test. A repair that restores that is money well spent; a repair that only defers the next fail is not, and the numbers usually make clear which you are looking at.
Questions
It depends why it failed. A discrete fault on a well-designed system usually justifies repair; a system that is old, inefficient, undersized or fundamentally misdesigned is often cheaper to replace over its remaining life.
The test report should say not just what failed but why. A specific fault - filter, fan, ductwork, damper - points to repair; a design or capacity shortfall that no component swap will fix points to replacement.
Only on the day. On a fundamentally inadequate system, serial repairs, re-tests and continued exposure risk can cost more over time than a properly designed replacement. The honest comparison is whole-life cost.
When the hoods are poorly placed, capture velocity is inadequate, or the system is undersized for a process that has grown - faults in the design itself, which repairs cannot cure.
Defaulting to repair every time because each fix looks cheaper, on a system that can never really pass. The individual repairs add up to more than a replacement while never solving the problem.
Have the failure properly diagnosed, then cost repair and replacement over the system's remaining life - including running cost and likely further failures - rather than comparing only the immediate invoices.
We will diagnose the failure and set out repair and replacement clearly, so you can decide on whole-life cost.
