There’s no doubt that small sensor systems can have an advantage over their cumbersome reference station cousins – in terms of maintenance requirements. We are often asked about ‘service’ requirements for our pods and the honest answer is that the default position, in normal working conditions, is ‘none’. However ..

There are consumables, conditions can have an impact and sometimes ‘stuff happens’. We have seen small sensor systems claiming they require no maintenance at all, so would like to offer some thoughts on these three areas:

Consumables

Some sensors and sensor components need to be replaced at a defined interval (two years for AQMesh). This may be because the product is designed to optimise accuracy and component duty cycle, such as the AQMesh pump sampling particulate matter, which is expected to last two years on standard settings. If the pump is not replaced at two years, in-field failure is the likely outcome at some point. AQMesh uses a pump to provide reliable sampling over a set period. An alternative, such as a fan, may not be offered with a finite duty cycle, or with one that is theoretically longer, but failure modes can be undetectable remotely and readings affected. Is that better?

Many small sensor systems use Alphasense’s electrochemical sensors, which come with a recommended two-year life. Sure, they last longer than two years and keep producing numbers, but who has tested the sensors beyond two years and will be answerable for accuracy after two years? Users of these systems need to look ‘under the hood’ here – is the system claiming to be maintenance-free ignoring sensor manufacture advice? Are they reducing operation or sampling to extend the duty cycle?

Monitoring conditions

In a nice, clean monitoring location it is possible to predict performance of a monitoring system over several years. But, when the system is faced with tough conditions – such as sandstorms or an acidic environment – some intervention may be necessary to keep the system running. Good design and remote diagnostics can help to minimise this, but it is often the pods installed in the most remote locations (hardest to reach if necessary) that are hit by the toughest conditions.

‘Stuff happens’

Most of the stuff that happens to AQMesh pods is hard to predict. One academic study, monitoring air quality around treated road surfaces, mounted pods a few centimetres above the road and they were swamped in a rainstorm. One contractor installed a pod on its side. Solar-powered pods are sometimes installed with great difficulty, only to find the system is constantly in shade. We encourage as much pre-installation planning as possible – and provide a wealth of manuals, guides and videos to avoid these scenarios – but there are sometimes situations which require on-site intervention. We have seen ‘maintenance free’ fulfilled by offering replacement equipment under warranty, instead of maintenance, but customers still have to make a site visit anyway, so we don’t really buy that one.

AQMesh started out offering uninterrupted 2-year gas monitoring with autonomous power but we quickly found that much monitoring was project-based and that users preferred to have the comfort of planned maintenance arrangements that would maximise the chances of achieving high data capture and high data quality throughout the project.

A UK local authority installed nine AQMesh air quality monitoring systems at different points across a busy town, measuring nitrogen dioxide (NO2) at 15 minute intervals, monitoring 24/7.

These locations were established monitoring points, where measurements had been taken previously using diffusion tubes, limited to one average reading every few weeks.

AQMesh – in common with all lower cost air quality systems – can provide near real-time air quality information, with high frequency measurements that allow daily and weekly patterns to be seen. However such systems are not certified, as are reference stations or diffusion tubes. As a result, AQMesh readings need to be ‘calibrated’ against certified readings, at some point in the network, to provide confidence in data accuracy and traceability to an approved standard.

Typically such ‘calibration’ is carried out by mounting at least one AQMesh ‘pod’ very close to a reference station, so pod and reference are sampling the same air and readings can be compared. However this approach does require staff to move pods from position to position, which can be time-consuming and therefore costly. An alternative approach was used for this network, similar to the one developed by the University of Cambridge and used in a major project in London (Breathe London pilot). One of the authority’s reference stations (location in red on map) was used to ‘calibrate’ the network of pods and the other (location in green on map) was used to cross-check network accuracy.

AQMesh network deployment (BELOW): AQMesh locations marked in blue, reference station used for calibration in red, reference station used for control co-location in green

The four-month project demonstrated that the AQMesh network showed that stakeholders could have the same high confidence in readings when the network was calibrated remotely as when pods were co-located for calibration (the gold standard for this technology), but with significant savings in field support and reduced data loss.

Is it normal to get excited about a Publicly Available Standard? For us it feels like a long time coming, and this first step on the long road towards an ISO standard for small sensor air quality monitoring is very welcome.

Whether you are using small sensor systems (with or without MCERTS) or reference grade equipment, you need a clear and agreed process for data, to show that data is trustworthy and reliable. PAS4023 is now freely available to the public to guide users on how to get accurate and valid data from small sensor systems. The standard essentially aims to provide a method for using small sensor systems which ensures any data produced is consistent and comparable to a known standard.

This takes a lot of the risk out of use of this type of monitoring equipment, especially where it has held back adoption in applications where it would add real value.

A QA plan makes all the difference. Without one, data is always open to challenge, however ‘good’ it is. If it can be demonstrated that a project is using the same equipment in the same place, at the same time, and following the PAS4023 document, data is more meaningful and can be used by government bodies.

In the 10+ years that AQMesh has been commercially available, it is the lack of this sort of clear guidance – put together by a team of experts – that has undermined confidence. So, a big thank you from us to the team behind the Standard.

Learn more about PAS4023 here and chat to us about how we can help you manage an air quality monitoring network you can rely on.

Autonomous power can make all the difference in hyper-local air quality monitoring. With particulate matter sampling needing a little more power than passive gas sensors, solar is the go-to power option, rather than internal battery.

Most systems require sufficiently little energy that they can be powered by a relatively small solar panel, but it’s the back-up power management that makes all the difference.

For much of the higher latitudes of Europe and North America, the challenge is to achieve full-year monitoring – just. What we want is to be sure that no readings are missed in December, but that we manage that without a huge solar panel or battery. Most small sensor air quality monitoring systems are mounted up lamp posts, so weight and size (wind resistance) are real considerations. As always, the devil is in the detail. Users should beware of ‘winter sampling’ settings, which reduce PM sampling during low solar power months, meaning each 15 minute reading may be based on as little as one minute of sampling. This is particularly relevant when the sampling regime is linked to certification, such as MCERTS.

AQMesh’s smart solution to powering air quality monitoring systems all year round

The AQMesh smart solar pack power supply option provides consistent, smooth and autonomous power all year round for an AQMesh pod. The pack is much more than just a solar panel, with the true benefit lying in back-up power management: it’s about powering the pod when the sun is not shining.

The solar pack is quick and easy to install – even up a ladder – and comes with flexible mounting options for posts and walls. Guidance is offered for safe, straightforward installation of the pod and ‘all in one’ solar pack, working at height. The solar pack is a compact unit with an adjustable angle for maximum solar harvest. Setting the direction and angle of the panel correctly at installation makes a significant difference to solar yield, even if no further adjustments are made for years. The simple single connection to the pod is the same as that used with the AQMesh standard weatherproof DC power supply, so solar can be easily interchanged with direct mains power, if ever required. The solar pack also features an additional connection to power a second pod at the same time, which helps when co-locating pods for short periods.

Smart functionality allows the charger to efficiently maximise solar harvest, maintaining battery health and extending the life of the battery. Using ultrafast maximum power point tracking (MPPT), the system monitors the voltage and current outputs of the panel to ensure optimum solar harvest during changing weather conditions and light intensity throughout the day. It also features an intelligent load output function with over-charge protection – preventing excessive drain on the batteries – and ensuring that a full 100% recharge will be attempted every day. Charging and battery voltages are among the key pieces of information that can be checked on site using a smart mobile Bluetooth app. Used by AQMesh and customer technicians around the world, quick access to information allows speedy diagnosis of any issues on site, and battery voltage information is also available alongside readings on the secure AQMeshData.net server.

Another consideration is the type of back-up battery used. Many systems use lithium ion batteries, which should not be charged – or re-charged, as a back-up battery – at temperatures below 0°C, with a recommended operating range of 15°C to 35°C, making them unreliable for winter solar back-up. Lithium ion batteries can also be problematic for shipping, with even a small quantity of lithium classed as ‘dangerous goods’, bringing transportation limitations and delays. The AQMesh solar pack uses an AGM lead acid battery, which has sufficient capacity, will continue to operate throughout cold temperatures and is easy to ship and replace.

This efficient solar charger means that even during periods of poor weather, the smart solar pack can power an AQMesh pod consistently – all year round – across the UK and Europe, based on standard measurement settings, with no need to reduce the sampling regime.

From Alberta to Scotland – and many points at lower latitude – AQMesh users around the globe are benefiting from uninterrupted power supply thanks to our bespoke and proven solution for autonomous, wireless power.

First of all, you can’t calibrate using bottled gas, as with reference analysers. Even if you can create a chamber or manifold to pump gases through, electrochemical gas sensors do not respond in the same way to single, dry gases as they do to mixed gases in an ambient environment. And that sort of ‘laboratory’ approach is even more difficult with particulate matter – we have seen huge resources devoted to mixing particles in a chamber, but it is very hard to achieve a known, consistent level against which to calibrate.

Small sensor systems are best calibrated by co-locating one or more units as close as possible to the intake of a reference or equivalence standard analyser, whether for gas or PM. Access to a reference analyser varies depending on the number available locally and also local authority policy regarding access. Mounting lots of small sensor systems in the confined space of a reference station is not easy, particularly finding clear space for power supplies, including solar. In this case, the ‘gold pod’ approach is effective: calibrate one unit against reference and then co-locate that unit against each of the others in turn, or with them all mounted together in a more convenient location. A couple of things to remember:

1. Some pollutants are poorly mixed, eg: NO close to source, so levels can vary dramatically over short distances: we consider a true co-location to be no more than a meter between sensor and reference inlet
   
   
2. Pollutant levels at the co-location site need to be appropriate – avoid sites where levels are very low, as calibration is likely to be unsuccessful and would result in low accuracy at locations where levels are higher

If a reference station is not available, diffusion tubes or passive samplers can be used instead. Both approaches offer traceability to a certified standard, and therefore provide a route for data quality assurance. We can provide a tested methodology for calibration against diffusion tubes.

As co-location as a means of calibration involves equipment movements (potentially many unit installations and de-installations), this approach can be resource-hungry. New methodology is now being used which can calibrate a network of small sensor systems against a reference station in the area, and is a service AQMesh offers.

A final word: beware ‘self-calibrating’ systems. If it uses machine learning for its data processing, then it will be optimised for the location and conditions of where it was calibrated, and the unit cannot be reliably deployed anywhere else with confidence in the calibration. In addition, the processing used to calibrate is not an ‘empirical correction’, so it is not repeatable or traceable to reference or similar instruments within its network.

AQMesh small sensor air quality monitoring systems have been in use around the world for over a decade now, but it remains the case that support challenges are always greater with ..

• New customers, unfamiliar with the product
• Located a long way away (distance, time zones, business culture)
• In difficult conditions (environmental, infrastructure)
• With little or no knowledge of air quality monitoring
• Working at the end of a long chain of parties

Whilst any one of these points in itself makes user support harder, the AQMesh team have energetically pursued the ideal of providing great support, even when all five challenges apply.

To illustrate this point, we can tell the story of 16 pods used in Bangladesh, Pakistan, Vietnam, Philippines and Mongolia. AQMesh was chosen for this project, funded by an international bank, coordinated by an international consultancy and procured through a UK distributor. The pods were shipped in April 2020 all measuring PM and a combination of gases including NO2, O3, CO and SO2 using mains and solar power. Most pods were installed easily, as AQMesh is designed for quick installation, by simply connecting the power supply and using the standard fittings provided to mount to a post.

In November 2020 two pods in Philippines were reported as ‘dead on arrival’. As the cause for this failure could not be quickly established remotely or through the chain of communication, two new replacement pods were shipped and it was confirmed they were functioning normally as soon as they were installed. Inspection of the two returned ‘dead’ pods indicated that the pods had been internally re-configured since they left the factory: this sort of curiosity is not unknown, and it is rare that any party wishes to hold their hand up, so the issue was not pursued further and all of those involved in the project were happy to see all pods delivering data. In February 2021 it was agreed that AQMesh would take over direct support of the pods, as it streamlined support by no longer communicating via the UK distributor.

By April 2021 some sensors had been replaced under the no-quibble 12 month warranty and the AQMesh team was explaining why data is redacted in ‘extreme conditions’. Briefly, all electrochemical sensors produce less stable output when subjected to high temperature and low humidity, often showing artificially elevated readings. AQMesh identifies and flags data under such conditions and the default is to redact flagged data, which avoids likely over-reads being reported. Even in the most extreme global environments, redaction leaves data delivery well above the 90% target set for conventional air quality monitoring equipment.

In September 2022 the international consultancy confirmed that their project had finished. The only way the pods could continue being used in the countries was through direct support from AQMesh, so the chain of communication shortened further and AQMesh offered to continue to support the pods, using the free weekly data delivery service.

To date the AQMesh team still supports the pods, free of charge, and recently resolved communication problems with pods in Pakistan which had been caused by environmental debris blocking the solar panels used as the power supply. One pod is now being returned to factory to be investigated, repaired and returned to the user.

AQMesh has always prided itself on its customer service. There is no cost for technical support and location continues to prove it is not a barrier. A wealth of online training material is provided in addition to remote technical support and smart remote diagnostics, including power cycling, re-stabilisation and sensor rebasing. Users also benefit from free remote firmware upgrades for the life of the product and free of charge data processing algorithm upgrades for gas channels, which means customers can be reassured they are always the using the most up to date technology available, giving them the most accurate and reliable data possible.

2023 is set to be a big year for AQMesh’s monitoring of particulate matter, with developments in both hardware and data processing offering improved accuracy across key PM fractions. AQMesh is also on the road towards MCERTS indicative certification, submitting data well above the required standard for indicative monitoring, and following on from achieving ISO9001:2015 certification in 2022.

The AQMesh optical particle counter already delivers high accuracy across PM2.5 and PM10, thanks to its proprietary design. The system also has the option to include a heated inlet – which has had a significant uptake during 2022 – to dry the sample prior to measurement and reduce the effects of moisture, leading to even more accurate readings.

AQMesh prides itself on its high levels of accuracy and reliability, and has already repeatedly demonstrated its performance well below the 50% measurement uncertainty required for indicative MCERTS for both PM2.5 and PM10 through extensive co-location comparisons across the globe, in real-world conditions.

The plot below shows AQMesh vs reference for PM2.5 at hourly averages during a one month time period.

Similar high performance can be seen for the more coarse PM10 particles, also at hourly averages over a one month time period, showing how AQMesh can provide more accurate results than nephelometers, which derive PM10, rather than measure it directly, as AQMesh does.

John Downie, Technical Business Development Manager for AQMesh, says “2022 has been successful for AQMesh, despite the turbulent times. We are pleased to have supplied pods to new regions this year, including Saudi Arabia, Angola, Latvia & Uzbekistan, further growing our already expansive global customer base. I’m looking forward to extending our reach even further still next year, especially as we look to achieve MCERTS & CEN certification. We have also seen huge interest in our bespoke smart solar pack – in fact, over 60% of our pod sales this year included the solar option.”

The AQMesh smart solar pack offers autonomous continuous power all year round for an AQMesh pod. More than ‘just a panel’, it features smart connectivity with a mobile app for checking power output, viewing historical data and running diagnostics.

The system continues to prove itself as fit-for-purpose flexible air quality monitor for a range of applications, including mining, construction, government agencies and transport operators. Pods can measure up to five gases out of NO, NO2, O3, CO, SO2, H2S and TVOC, as well as an additional CO2 sensor, and PM1, PM2.5, PM4, & PM10. These are all fitted in one compact unit, with various autonomous power options and seamless data delivery Wind speed & direction and noise monitoring are also available, with humidity, pressure and pod temperature included as standard.

2022 marked 10 years of innovation and leadership from AQMesh. To highlight the team’s experience, ongoing forward-thinking and its commitment to pushing the capabilities of small sensor systems, here are the top 10 things AQMesh developed first and refined since it commercially launched in 2012.

1. IoT connectivity using the mobile phone network: remote data for small sensor air quality monitoring

AQMesh was the first small sensor manufacturer to adopt an IoT approach, using the mobile phone network to connect with the cloud, allowing remote access of data from individual measurement points. Until then, conventional equipment used loggers and other early small sensor air quality equipment offered direct download or radio communication, often across a group of sensor nodes.

2. Integration of gas and PM monitoring in a single small sensor instrument

Since 2013, AQMesh pods have been able to monitor gases and particles in one instrument. The compact pods have continued to lead in terms of the wide range of measurements offered on a single unit: up to six gases out of NO, NO2, O3, CO, SO2, H2S, TVOC and CO2 as well as PM monitoring and options for noise and wind speed/direction. Pressure, relative humidity and pod temperature are all measured as standard. In the 2019 AIRLAB International Microsensors Challenge, AQMesh was recognised as the most accurate multi-parameter outdoor air quality monitor, and was evaluated for the highest number of pollutant measurements offered within a single system.

3. Mini optical particle counter, counting and sorting particles by size, for accuracy across all PM fractions

AQMesh’s in-house designed optical particle counter measures particulates PM1, PM2.5, PM10, TPC and TSP (up to 30 microns). Its bespoke design uses a straight line between the sample inlet and bench, meaning larger particles do not settle in a bent sample path, allowing for complete capture of pollutants. Additionally, the OPC uses a pump instead of a fan, which produces a steady flow from inlet to sample measurement, and subsequently provides consistency for the sample calculations – fans can cause vacuums which could interfere with the flow rate and affect the sample measurement. The AQMesh OPC therefore allows more coarse particles (PM10) in the sample to be accurately measured.

4. Pioneers of city-wide small sensor networks from Citi-Sense to the Breathe London Pilot

Initiated in 2012, AQMesh was part of the EU-funded consortium which set up a ground-breaking project to advise citizens about air quality, across eight cities, using hundreds of measurement devices. The Breathe London pilot, which ran from 2018 to 2020, and in which 100 AQMesh pods were used, was the world’s first hyperlocal monitoring network. The two year pilot project proved & validated small sensors for city-wide monitoring, and also led to the Environmental Defense Fund (EDF) publishing a ‘blueprint’ for other cities.

5. Real-time out-of-the-box accuracy with correction for environmental conditions and cross-gas effects without the need for machine learning

AQMesh’s high accuracy and performance has been achieved through years of extensive global co-location comparison trials against certified reference equipment, in all seasons, meaning AQMesh can accurately operate in the widest possible range of environments and conditions. No other manufacturer has access to the wealth of data that AQMesh has gathered. With these datasets AQMesh has been able to develop meaningful correction of cross-gas effects and interference from environmental conditions through its fully traceable data processing algorithms.

6. ‘Gold pod’ approach

The ‘gold pod’ approach, as originally described by the AQMesh team, involves one unit being co-located with and scaled against a maintained reference station and then moved around a network of nodes to calibrate each of the other units. This method has now been widely adopted and offers an effective way to improve accuracy and achieve traceability. It was back in 2017 when Professor Rod Jones from the University of Cambridge presented the results of the ‘gold pod’ approach in which 20 AQMesh pods were deployed across Cambridge after co-locating one with reference, and he commented at the time “Because we know that all the pods read the same and because we have a comparison between one pod and a reference instrument we can say that all pods are working equivalently across the city.”

7. White reflective sunshield and insulation for temperature management

The sunshield was first added to AQMesh pods in 2013 to minimise the impact of direct sunlight on pod sensors. Various solutions were tested – for active or passive cooling – and AQMesh’s reflective shield, insulation and air flow gap was found to be most effective at minimising the challenge to temperature stability from strong, direct sunshine.

8. Promote rigorous QA/QC and offer feasible methods to achieve it

Since 2015, the AQMesh onsite reference station means each sensor has been tested through a rigorous quality control process before it leaves the UK factory. The custom-built enclosure uses climate-controlled reference/equivalence analysers sampling air from an ambient cage which can hold up to 100 AQMesh pods at a time. This ambient characterisation during manufacture is part of a stringent AQMesh quality assurance process, which also includes strict criteria for PM, so every AQMesh pod out in the field to date has been through specific quality control measures to ensure the efficiency and reliability of each sensor in real-world conditions. QA/QC doesn’t end at the factory either; the AQMesh team regularly offer remote QA/QC of data once pods are out in the field.

9. CO2 emissions profiling

AQMesh can offer incredibly high out-of-the-box accuracy (typically less than 15% uncertainty) for CO2 monitoring. Using this reliable data, AQMesh can be used for CO2 source apportionment, and measuring alongside NO and NO2 can allow for emissions profiles for different locations to be determined. This means the combustion contributing to the pollution can be specifically identified; such as whether there is either gas or diesel traffic, which is only possible with such accurate data.

10. Long distance scaling

The Breathe London pilot showed how pods could be traceably scaled across a city, using a novel approach pioneered by partners at the University of Cambridge. This technique, which reduces the field demands of the proven gold pod approach, requires basic measurement data of a good quality in order to be effective, and AQMesh have built on the initial Breathe London methodology with their own simplified Long Distance Scaling tool.

AQMesh is one of three winners of the Air Quality & Sport Challenge, an initiative by ThinkSport whose aim is to create solutions to help sport organisations tackle climate change.

The Challenge is a collaboration by ThinkSport, together with the Sustainable Sport Lab (SSL) and the Sustainable Mountain Alliance (SMA), and supported by numerous stakeholders including the International Olympic Committee (IOC), World Athletics and Formula E.

AQMesh was presented as a solution in the category for measuring and mitigating the effect of poor air quality on athletes, and it is able to offer its benefits of real-time hyperlocal pollution data as a compact and flexible platform in order to report on the key pollutants known to affect human health and athlete performance.

John Downie from AQMesh will be attending The Spot – ThinkSport’s flagship international sport and innovation event – in Switzerland on 17^th & 18^th May, where each winner will be able to showcase their solution.

AQMesh has been commercially available since 2012 – making it the most proven and relied upon small sensor system on the market. During the last ten years, the team at AQMesh has never stood still by continuously improving the design and functionality of the product in response to the many challenges that localised air quality monitoring has presented around the globe.

Originally launched as a pod which could monitor only three or five gases, AQMesh has evolved over time to offer a single, compact system that can measure up to six gas pollutants from a choice of seven and particulate fractions including PM1, PM2.5, PM4 and PM10, along with additional options for noise and windspeed and direction. A range of autonomous power supply options have been developed to suit almost any monitoring location, supported with seamless data delivery via the completely secure bespoke-built AQMeshData.net server.

The team have been able to continually demonstrate and prove the product’s high quality performance in more environments and locations than any other system. Using extensive global co-location comparisons now spanning over ten years, the AQMesh team have consistently improved and developed sensor performance against certified reference / FEM equivalent methods and validate small sensor technology for air quality monitoring applications.

Access to their own onsite reference station means the AQMesh team is able to test each sensor individually through a meaningful and rigorous quality control process before it is installed. During this process, the sensitivity of each sensor to the target pollutant is measured against the reference equipment and sensors which show a response outside the defined range are rejected. Traceable adjustments can also be applied to optimise consistency, precision and accuracy through AQMesh’s proprietary data processing algorithms.

Having been established for longer than any other platform, the team has also been able to continually review the product’s long-term performance. Baseline stability of AQMesh’s electrochemical sensors has been continually proven over many years of independent global co-location trials against certified reference equipment. These trials have also enabled AQMesh to be tested in the widest possible range of real-world applications, environments, seasons and climates. AQMesh pods have continued to operate under snowy conditions in Sweden, Minnesota and Iceland, in the scorching heat of Iraq deserts and in the heavy, humid rainfalls seen in Asia. The expansive range of countries that AQMesh has been used in has helped the team lead the way in small sensor air quality monitoring system design and ensuring the product is fit for purpose in every possible environment.

The AQMesh team has built strong relationships with reputable global partners over the years and has fully trained them to support AQMesh in their local regions, meaning that location is not a barrier to supplying AQMesh. Through this well-established network of authorised global distributors and AQMesh’s own remote support, the AQMesh team pride themselves on the high level of customer service and technical support it can offer its users wherever they may be.

Another of the many benefits of choosing AQMesh as your air quality monitoring solution is its low cost of ownership. AQMesh pods have been developed over time to require minimal maintenance and there are minimal ongoing costs. Electrochemical sensors and consumables for our filter-free particle counter are recommended for replacement every two years, and all consumable sensors are replaced for free during the first year if necessary. AQMesh was the first small sensor platform to offer a 5-year warranty, and there is also a free data access service option, allowing suitability to any budget. Customers are able to use their own local M2M SIM if they prefer, although AQMesh’s global SIM contracts give fantastic worldwide coverage and are reasonably priced, offering fixed costs and added convenience.

AQMesh has always been at the forefront of the small sensor air quality monitoring market, investing in extensive testing and development that has paved the way for other manufacturers to follow in its footsteps, as well as defining data validation methodologies and providing blueprints for deploying city-wide networks. The team continue to research, test and develop AQMesh and push the limitations of small sensors to ensure the product remains more than fit-for-purpose and offers value for money in an increasingly competitive market whilst still retaining its core principles of proven high quality data, accuracy and unbeatable customer service.