Hi I wonder if anyone can assist. I work in a print factory. There is a residential estate situated in close proximity. We Work 24 hours From Sunday 22:00hrs to the following Saturday 06:00hrs.Every Summer we have a resident that comes and complains about the noise during the night from our extraction fans during the warm weather.
We have tried to abide by his wishes but he still complains.
Can anyone tell me what the maximum noise level should be before it becomes a noise nuisance and the Local Council gets involved. I have searched the web but can not find an answer.

There isn't a maximum level, what would be acceptable in a town centre would be horrendous in a rural location. So......
As a very crude rule the council (normally Environmental Health) if involved will compare the noise levels when the plant is/is not operating. A difference between the background level (L90) and the noise source(Leq) of around 5dB is considered possible to cause complaint, and a difference above 10dB is likely to justify any complaints.
Remember noise is a log scale so every 3dB increase is in effect a doubling of energy.
May be worth getting hold of a specialized consultant/advisor to see if proactively anything can be done. Sometimes solutions can be very simple, conversely, it can also cost a lot of money to mitigate.

You may find the council will not be that interested, especially if you have tried to mitigate the problem already.

I seem to remember from my environmental training that also more leeway is given if your business was there before the housing estate. So he bought a house near you.

If you want to keep the natives happy, there are things you can do to help with the noise, but depends on the layout. Fences / grass banks /bushes will absorb and reflect noise. Higher up trees can also help dissipate noise (Google it).

My local council were at one point going to allow a methane powered generator near to a village where I live (across the road from a new housing estate and about 1/4 mile from me) and that would have been 65 db day and night 7 days a week. It was stopped, but not on the noise issue.

Also make sure you are the one creating the noise. Where I previously worked we had a complaint against us and when the council visited it turned out to be the local Tesco's (other supermarkets may also make a noise at night).

Chris

In a previous employment... We had persistent and increasingly irate complaints from a couple of local residents about our persistent fan noise. We had a large factory with literally dozens of fans and compressors working 24\7. Eventually, on site, two am with the local EHO... We traced the offending monotonous pure tone humming to a small air pump in the back garden of one of the complainants. Used to inflate his greenhouse poly tunnel. Red faces and profuse apologies! (But I did enjoy the nocturnal activities of the local fox population whilst trying to track the source. They weren't in the least disturbed by the noise!)