As solder fume extraction is an LEV system it requires statutory inspection by a qualified person at a maximum of every 14 months to ensure it is achieving the required capture rates and flow. I noticed you didn’t mention that it had been received its statutory inspections and was in date and validated as working effectively. Although you did mention it is maintained in house and you have completed some exposure monitoring. This isn’t the same as statutory inspections for ensuring the correct operation of an LEV system.

A decent LEV company would normally notice potential issues caused by such things as Air con systems interfering with either the extraction rate or diverting the path of the fumes away from the extraction.

The air con must be very close or very powerful to be overriding the extraction in the first instance as the pipe drawing the fumes away are normally so close to the work operation if not itself fitted to the soldering tool. Could a deflector be installed below the aircon to direct the flow it away or diffuse the flow.

At the end of the day there are always going to be complaints when it comes to air con/heating issues and different peoples comfort levels, and it normally transpires with great difficulty that these have to be managed as well. However,  you have a higher duty of care regarding the management and capture of fumes and vapours which are potentially harmful to your employees.

Tangoswift

Something to consider as most companies conduct their LEV inspections every 12 months as opposed using an odd number of months is that you get no rotation over time to cover the changes of the year. If the inspections are conducted in December and the Air Conditioning is not used for heating purposes then the effect upon the LEV extraction can be missed as the tests are always conducted at the same time of year when the air con isn’t running. 

As it stands you will have to address to your employees’ current concerns until you have exhausted all efforts to ensure that you have achieved what would be considered as reasonably practicable. 

Keep up the LEV Inspections and maintenance and ensure the layout of the area hasn’t changed since the exposure monitoring was last conducted which might have affected the result.

The root cause is NOT usually found to be the complainant when it comes to health and safety when a root cause analysis is conducted properly, although some employees who enjoy testing the resolve of their employer can require what might be considered as more dynamic management requirements that others to put it politely.

As you have appeared to have covered everything e.g. maintained the system, had it statutory inspected, and conducted exposure monitoring, you may have already achieved the above (Reasonably Practicable).

Try explaining this to your concerned employee as you issue them with a half face mask which will be face fitted telling them as they have concerns and you have done all that is reasonably practicable, you are down to your last resort in a health and safety regarding hierarchy of control and that is the use of appropriate PPE.

You don’t have to enforce the wearing of such masks as exposure monitoring has identified there is not an issue and explain this to all employees but make the masks available to persons who might be concerned explaining that they are provided to give them if they wish to use them additional piece of mind and watch how the concern normally soon evaporates into thin air.

Which came first soldering station LEV or air-con?

If the air-con came afterwards was its design & installation considered so as not to interfere with the LEV?

Then the list of ususal suspects:

1) The LEV test is like an MOT fine in the hands of the tester (especially where they were also the designer, installer & maintainer) on a specific day and subject to abuse/miss-use in the intervening period.

2) Air-con running at maximum draw during LEV test? Or was the air-con off  / set to low?

3) As you mention several operators are they all correctly using the LEV or do you have a mix in skills and application technique for example pushing a swing dust to one side as it was designed for a right hand operator when the employee is left handed?

4) Is pipe maintenance conducted en-mass (especially with a single extraction fan) or do the engineers work one station at a time potentially having open ends (problematic where there is a common group of vents)?

Remember half face fitted masks are not the only RPE solution

Fully appreciate where the comment came from and its intended outcome.

In these days of inclusivity, anti-harassment and anti-bullying we need to be careful how we walk on egg shells.

an example of egg shells then appears via Police Scotland https://www.bbc.co.uk/news/uk-scotland-67005300

Can I ask what the LEV testing consisted of? A lot of what is described as LEV testing essentially  consists of checking  what level of suck a particular LEV can achieve. This might be useful but  much better is testing to establish if the LEV actually protects the operator. This should be done under real working conditions including this like the aircon running. Has the testing company done any smoke testing?