Before and After



Rogues Gallery

Free Health Check


Bad NO2

Free Calibration Spreadsheet



Air Quality Data Management (AQDM) and Geoff Broughton can help you collect and process your ambient air quality data. Most air quality data processing is routine. Scaling raw measurements into concentrations using the latest calibrations and eliminating bad data requires the right software or spreadsheet. This will produce a good dataset fit for your Annual Summary Report (ASR). Problems may surface if you are brave enough to put your data on a website or show timeseries charts in your published reports. The data should advertise your work and not become a potential source of embarrassment!






Real-time and historic information are displayed on a set of air quality websites.

Air quality data for all the sites across the UK

Cheshire West and Chester air quality network

Liverpool Air Quality Monitoring Network

North Lincolnshire air quality network

Norfolk air quality network

Nottingham air quality network

Southampton air quality network

Drop me an email if you like this website

A good looking final dataset is far more important than how well you ran the project!

Data management costs are small in comparison to the operation of your monitoring site.

Keeping on top of data issues is no more expensive than allowing performance to slide.

Here are some good reasons to contact me.

  • I can process your data better, faster and cheaper.
  • You don’t have time or enough monitoring stations to become a full time expert.
  • I've processed the data for more than 2,200 automatic sites since 1982 working at AEA, NETCEN, WSL and AQDM.
  • You don’t need to solve problems that I have seen many times.
  • I can review your final data and show you what you need to correct.

Test yourself with the Before and After and the Rogues Gallery and see if you can do better.

You need my help if you think nothing is wrong.

Here is a simple everyday problem. How would you process these NO2 concentrations?

  • Delete the negatives?
  • Replace the negatives with 0 ppb?
  • Add 5 ppb to the NO2?
  • Decrease the NO sensitivity by 2%?
  • Replace the charcoal scrubber?
  • Replace the three-way valve?
  • Perform a GPT?
  • Replace your service engineers?
  • Recertify your poisoned NO cylinder?


Get this wrong and the problem is never fixed, your reports become visibly suspect, the NO2 diffusion tubes are wrongly biased and your Action Plan is undermined.


No data is better than wrong data.

How can the NO2 measurements go wrong?


Click here is see a simple worked example and the dramatic effect of typical instrument drift.


A tiny 1% error can easily overestimate the NO2 concentrations by 10%!

How many AQMAs have been declared or not declared based on suspect data?

How often have the NO2 diffusion tube local bias adjustment factor or the AQ models been doubted?

You need an expert to check, select, smooth and apply the best calibration scalings to your measurements.

Day-to-day operations require you to identify the problems.

Final data ratification requires you to understand the problems.

Day-to-day data collection and fault identification can be learnt by a training course and some practice. You just need to call-out the engineer promptly when you see something has "gone wrong". But how do you process the data based on the engineer's technical report? You need to understand what went wrong to either ignore, delete or correct the data.

There are numerous ways that instruments and calibrations can produce poor quality data. Some are so rare that you are unlikely to ever experience the fault in your network. You may struggle to diagnose the new problem and make the right decision but your final data and statistics must look good. Breakdowns can produce high peaks that exceed the air quality limits and dramatically affect your reports. How do you know what is good or bad?

Why bother recording the instrument diagnostics?

The instrument diagnostics are often hard to interpret and even the engineers do not always understand the significance. Above is a typical calibration spreadsheet for a ML 9841B NOx instrument. The operator has made a comment and the Chassis temperature was hot on arrival. So what? The carbon scrubber on the NOx exhaust needs to be changed to prevent ozone leaking into the enclosure and, more importantly, damaging the pump valves. The service engineer will probably want to replace the scrubber now rather than wait for the pump to fail.

The instrument chassis temperature was hot on arrival then cooled to normal while the enclosure door was open. Perhaps the ventilation grills need cleaning and the cooling fans need to be checked. NOx instruments can go crazy during hot summer afternoons which reduces the life some expensive components. Fix the cooling now before too late.

I have decades of experience examining data from hundreds of operational sites and thousands of closed sites. I can readily spot anomalies, diagnose the problem and make the appropriate correction without unnecessary data loss. Here are some typical corrections that make a huge difference to your data and annual statistics.

  • Ramped (proportional) zero and sensitivity scalings.
  • Rescaling ozone sensitivities after a photometer test.
  • Correcting NO2 converter inefficiencies.
  • Correcting for BAM and TEOM low flow rates.
  • Correcting TEOM k0 anomalies.
  • Rescaling poisoned calibration cylinders.

Applying the final polish to your data is not difficult or expensive if you know what can go wrong.

I can help you produce high quality data and statistics in several ways.

  • Processing the data you have collected.
  • Calculating your statistics.
  • Training you to spot unusual faults.
  • Reviewing your processed data and suggesting a course of action.
  • Showing you how to create a Ratification Production Line to meet deadlines.
  • Creating a Quality Circle that pools your knowledge and drives forward improvements.

The cost is small in comparison to the operation of your monitoring site. You have spent an enormous amount of money on instruments, cylinders, cabins, site visits, calibrations, service contracts, spare parts and data collection. All this is wasted if you skimp on a few hundred pounds for the final expert data ratification and report dodgy data.

I'm always happy to discuss air quality data and provide free advice.

Contact me

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