Indoor Air Quality Monitoring – using low cost sensor and standard methods

As people return to work after covid lock-down, many were concerned as to how clean their office was. They deployed many types of monitoring methods.

For a number of organisations this meant, operating in a field that they new little about and purchasing equipment on line that was neither suitable for the application, had no validation(Mcerts)  or calibration.  They had no knowledge on a reporting standard that they required to meet, nor what that would mean

Other groups of people are seeking to get a certification for their building, such as Breeam, Well, LEED

When perform Indoor Air Quality(IAQ) we can define a number of key pollutants that we can monitor. These include:

NO2- Nitrogen Dioxide

PM10, PM2.5- These are particulate matter (PM) with a size of , either less than 10 microns (PM10) or less than 2,5 microns

CO2 -Carbon Dioxide

CO, carbon Monoxide

Temperature and relative humidity (RH)

Formaldehyde – This is a basic set of monitoring that can be done within a building.

Of equal importance is : What are the sources of these pollutants and how do we mitigate for them.

Where do we sample from ( our sampling location ) and for  how long and at what rate?

What do are results mean and what do we compare them with . can provide monitoring equipment that is accredited – provides consultancy to monitor for these

ArmiteMini H2S
Airmite Mini H2S from EM-monitors

New Hydrogen Sulphide PPB Monitor

Traditional the most accurate way to monitor for hydrogen sulphide was using the Arizona Instruments Gold Leaf Monitor or the Honeywell SPM toxic gas detector. Today this is still true, these techniques are still the most accurate. However other technologies are gaining ground.

The newer technologies have the advantages of being:

a, Continuous

b, Affordable

c, Remotely monitoring to a data dashboard with csv file download

We now Supply our Airmite mini H2S with

real time monitoring of H2S at the ppb level (range 5ppb to 20 pmm).  it also measures:

real time pm10, pm2.5 and pm1

real time Humidity and temperature

GPS location and 4G remote connectivity or ethernet cable connectivity

This is instrument is ideal for waste water treatment, odour monitoring, or nuisance monitoring of hydrogen sulphide odour

ArmiteMini H2S
Airmite Mini H2S from EM-monitors

Monitoring Office Air – New Building Air Quality Monitoring Confusion

Technology is moving on in leaps and bounds. We are now able to switch on our home TV on whilst traveling in our car. All so that Twicki your pet hamster can watch Brooklyn 911.

We are now capable of building an array of sensors that can measure all manor things. These sensors are now being fully integrated into our home and work place. From heater controls, HVAC controls, security cameras and much more in the intelligent building.

The field of Indoor Air Quality Monitoring has become a real eye opener. Where does this requirement come form ? Many of the Millenials want instant data, acquired to a phone App. Instant gratification. Knowing what the air in the room you are in consists of

The other drivers are things like BREEAM, WELL and LEED. These certification schemes afford credits to buildings that are built with the ability not only to minimise the amount of hydrocarbon in the building but also to monitor total hydrocarbons and other parameters such as fine particulate (pm2.5 – fine particulate has a diameter of less than 2.5micron, which means it is respirable). Other items include:

Nitrogen Dioxide (NO2)

Total Volatile Organic Compound (TVOC)

Carbon Dioxide (CO2)

Carbon Monoxide (CO0

Relative Humidity (RH)

Temperature (T)


The huge issue here is that there are no standards or certification for Indoor Air Quality Monitors. Most companies purchase an unvalidated products to put in their “Smart Building” These are simply not viable. Most of this type of product is garbage purchased on line.

To put a simple perspective on it, if you felt unwell you would go to a doctor, you wouldn’t go to Asda and ask the person in groceries to provide help? They would sell you an apple!

So why would you do it for incredibly specialised equipment.

Airmite Em-monitors
Airmite Smart monitr

A recent study identified shortfalls in the mass market air quality sensors

Formaldehyde and Total VOC (TVOC) Commercial Low-Cost Monitoring Devices: From an Evaluation in Controlled Conditions to a Use Case Application in a Real Buildingby

It states the response of the sensors was in many cases a lot lower than required , linearity was poor as was repeatability and reliability. For example Formaldehyde is a very specific hydrocarbon. There are specific iso methods as to how it is monitored. To identify it amongst a range of other hydrocarbons using low cost sensors may be duplicitous

There are new sensor which, are primarily used for the air quality market but also good for the indoor air quality market.

Environmental Monitoring www, and have spent a long time looking at these issue. Working with partners at the HSE and SCS. We now have Mcerts Accredited air quality monitors. As well as an accreditation, they have been co located and type tested again Government run reference monitoring systems ( reference systems cost in the region of £100, 000)

Good  professional install air quality monitors cost between £3,000 and £6,000 . They are accurate and precise.

However these units have to be carefully installed, at the correct height, with power and the data must be managed. Not only the data but the servicing and validation of the equipment.

For information of types of monitor and



Airmite mini Dust plus 1 gas
Airmite Mini Smart compact remote dust and gas monitor




Air Tight Building Issues

em-monitors pid years ago Environmental Monitoring were asked to review the air quality within a new building just of the north circular in London. We went in with a blank sheet. No pre-conceptions of the how the house was constructed.

The owner had purchased the house for several million pounds but felt that it was not possible to occupy the house because there was and i quote “no air” in the house.

As part of the local authority building requirements, the building had to be designed to not only be airtight but also to have an active filtration system.

We provided the client with a full suite of monitoring equipment for hire including

Indoor air quality monitoring for :

Carbon Monoxide

Carbon Dioxide


Relative Humidity

Ambient Pressure

TVOC ( total volatile organic monitoring)

Particulate  aerosol sampling

Microbio sampling

Airflow monitoring

We also provided an independent review of the premises .

What was discovered –

Carbon Dioxide CO2 readings were typically around the 1500-1800ppm range

Relative humidity was 68-69%

Air flow was negligible

Ambient temperature was in the range of 23-25 , without any heating operating

internal ambient pressure was greater then external ambient.

Upon closer investigation, when we reviewed the filtration and air distribution system. The manual from the manufacturer stated that the ducting should be smooth bore rigid tubing. However the electricians that fitted the system used corrugated, flexible tubing. Upon removal it was found to be loaded with mould. The perfect distribution system.

To summarise . In trying to solve one problem. That of heat loss and heat inefficiency, it appears other problems have been created. Mould appeared in rooms without any explanation.

There were many problems, exacerbated by a poorly installed and not understood air filtration/ distribution system

Giving rise to :

  1. Poor Air Flow
  2. High Relative Humdity
  3. Mould Growth

The equipment used was a mixture of real time calibrated indoor air quality monitors . All the equipment was of a professional standard. Calibrated prior to the test it included :


Mini RAe 300 pid

Dusttrak DRX

MB2 Microbio sampler

Druck 750 pressure monitor

Kimo-instruments air flow

all supplied by Environmental Monitors it is important to note that modern home monitors tend to under report many of these issues. Each of our instruments cost several thousands of pounds and are regularly calibrated. That said we good observation and fresh air “rinsing” you can build a reasonable picture of your home environment using a cheap device

Smart Air Quality Monitors- We are moving in the right direction but..

We currently live in a world where we are able to access a myriad of facts, all a button click away on our phones.

We then enter beautifully manicured websites promising us a utopic world where everything can be monitored and then be directly read to an app on your phone.

The good new is we are getting cost effective monitors that we can carry around with us or use in the home but…. what are they reading.

I have spent most of my life working in air monitoring. In order for a product to give you some information that you can look at and trust you need to have a set of rules to to help define what it is you are looking at.


For example when you buy 5 kg of potatoes in a sealed bag – you either trust your getting five kg or you don’t care you just want spuds. The 5kg comes from the fact that the potatoes have been weighed. We know the weight is correct because at some point in the day, or week a calibration weight of 5kg is placed on the scale where they are packed and the scales are adjusted to be accurate.

This applies to any measurement we take. The thermometer at your doctors, or the speed camera used by the police.

Many indicative monitors don’t have this, though some do

Professional Reference Monitoring equipment would typically cost around £100,00.00. it would use reference monitoring techniques. However it would be used as follows:

So as you see it is all quite complex. lots of checks.

Moving down below reference equipment is cell technology. It is small and compact. it is what we are seeing out on the street now and in a myriad of pretty boxes for the home. Some of these are accredited and some also have very serious algorithms to correct their functionality. These are professional use tools and cost £3,000 upwards.These are Indicative Monitors. There are also more basic home use indicative monitors

Indicative Monitors

But be careful, many of the Chinese imported products are simply garbage and will respond to anything.

What do most of the Indoor Air Quality Monitors Do well?

  • Relative Humidity (%RH)
  • Temperature
  • Air Presure
  • Carbon Dioxide

Areas where they tend to perform poorly

  • VOC’s most commercial voc monitors require regular and careful calibration, VOC’s can include anything from Formaldyde , to perfumes & deoudorant
  • Nitrogen Dioxide (NO2) – product of combustion
  • Fine particulate – respirable dust PM2.5

in test we conduct with a calibrated reference the budget indoor monitor typically showed results 10 x lower PM 2.5 than an accredited calibrated tool. Other items simply did not respond

So there is a reason why tested monitors cost £1,000’s and basic ones a lot lot less. This should change with the emergence of goods British Standards.

In the meantime, rather than look for specific numbers , look for trends. That is significant changes in the air quality

Workplace Exposure Monitoring & Training


Environmental Monitors(see have been offers a new affordable workplace exposure monitoring service that our clients appear to like .

Traditionally a company would invite a consultant in to physically perform a survey of the workplace. For medium to large companies, this tends to work well. A professional service is offered, a report is duly submitted and recommendations are made.

Our aim is to put the person responsible for workplace exposure monitoring with the organisation into the shoes of the consultant. In doing this we begin a journey for:

  • knowledge
  • process
  • exposure limitation

For this example we will consider inhalable and respirable dust

We offer:

  • Training
  • Methods of monitoring compliant with HSE requirements (MDHS methods)
  • The latest workplace exposure monitoring equipment to comply with the standard
  • Calibration of the equipment
  • Supply of preweighed filter medium
  • All filters and media are from a UKAS accredited laboratory
  • Basic report turn around time 2-3

We provide all the necessary knowledge, equipment and test materials to enable you to perform a test. Once the test is complete a report is issued approximately 2-3 weeks later.

The report will contain a summary of result, calculation to give a concentration and a 8 hour TWA ( time weighted average)

For further information please contact :


Tel:      01539 727878

Mob:  07799626406







Affordable, accurate air quality monitoring for private individuals

It had been the case up until very recently that the only way to monitor the air was using  reference monitoring equipment, normally house in large steel containers. This is still the case. For those organisations who are required to report as part of the AURN(automated urban and rural network) then large reference analysers which are regularly maintained and calibrated is now the case.

However,what if you needed to to have some kind of indication as to how they air changed within your location and that it was reasonably accurate.

This is where the indicative monitoring market become useful.

Indicative Monitors

Indicative monitors tend to use low cell technology as well as low cost laser, Ir and pid technology.

what can they measure. (I will tell you a bit more about these pollutants and where they come from later)

Particulate Matter

PM10, PM 2.5 and PM1

CO- Carbon Monoxide

CO2- Carbon Dioxide

NO-Nitric Oxide

NO2-Nitrogen Dioxide

SO2- Sulphur Dioxide

Airmite mini Dust plus 1 gas
compact remote dust & gas monitor

They are now in an affordable range to the person in the street,

What do we mean by affordable and how good is an affordable unit?

This is where a bit of a minefield opens up. There are many many variants of product on the internet. Having worked with major consultants and the HSE it is now quite apparent which products are useful

Quality vs Quantity

The products we use and test tend to fall within the price range of £3,000 to £6,000. The price will vary from unit to unit depending on how it is configured. A unit that can monitor one gas and particulate matter only would be at the lower end of the price spectrum as compared with a four gas and particulate unit.

My words of cautious are :

1,beware purchasing any  product for a specialist project that isnt sold by a company who is conversant  with monitoring for pollutants

2, Many low cost units do not measure the parameters they state the will measure. For instance we compared a budget £400 product with a £5,000 product and introduce test gases into the budget product and the higher priced unit. The higher priced unit showed good correlation with the test gas. The budget one – did not register

How might you use your date?  when you look at many government sites, it some becomes apparent that the data for different species are averaged according to different requirements. So it is important to understand how your going to average it.

Finally and very importantly – why are you doing this work? if it is important, we would recommend that you work with your regulating authority and establish with them a firm objective of what you are trying to do . This is difficult. they may have another political agenda.


What other features may be important:

A Data Dashboard – This often requires a yearly subscription to the company that hosts your data.

The data dashboard should show time based trends including peaks and averages. it should allow you to down load data into a spreadsheet.

Status: Information of the unit will be provided by the supporting company, whether the unit is online or if it has a fault

Particulate Matter : Two types of sampling are currently available : Analysers with heated head inlets and those without. The ones without require a very specific algorithm in                                    order to ensure that moisture droplets are not counted as particulate. In order for this to occur the temperature and humidity of the sample also needs to be measures                                            separately

GPS                         To enable the location of the unit to be shown on Google maps or similar


Wifi                         To acquire data that you can see on the data dashboard , the instrument has to communicate via wifi. You will need to ensure that you know what company supplies the best                                   wifi coverage in your area for 4G. You will need to supply a SIMcard for this, we normally install this on your behalf

Power                     The units can typically be powered from a 7-24vdc source, 110v ac or 240V. It is always recommend that a circuit breaker be used. There is also a solar kit, which requires a                                        large lead acid battery to be used with it. This is good for sunny climates

Installation            Most of our units are supplied with a post/wall mounting kit. It typically takes 30mins to get up and running


Servicing & Cell Replacment

This typically occurs every 2 years sometimes longer depending on the environment the monitors have been in and the status of the cells/laser


Examples of Monitoring Diesel Vehicals

Roadside Monitoring or vehicle emissions. The most basic form of monitoring would be the requirement to monitor particulate, However not just the total Inhalable particulate. We also are required to monitor the fine particulate, the smaller sized 2.5 micron (pm2.5) and less. This is respirable dust and very harmful

As well particulate other gases which are associated with diesel engined vehicles are NO2 (Nitrogen Dioxide) and NO(Nitric Oxide)

we are currently in the process of finalising the development of a two gas and dust sampler for this specific application


Where Next : Once you have  acquired data, you might wish to compare to national standard or european standards. Please note these are indicative levels not reference levels, but they are good to be used as to highlight an area of concern

Further Reading





I hope this brief guide has helped

please contact








Air Testing & Air Monitoring – services and devices

c;lean air monitring

Environmental Monitoring is a UK leader in the supply of equipment, training and advice in the following areas:

  • Workplace exposure monitoring – with reference to air and noise monitoring. We offer a unique service of hire with technical support.

This enables you to obtain a full workplace exposure monitoring report, complying with the HSE monitoring requirements, whilst gaining greater in-depth knowledge of the monitoring system. It is also a more cost saving approach to monitoring


Kendal’s Mint Cake Fresh Air

c;lean air monitring

We have three things in abundance in Kendal in Cumbria:


Kendal Mint Cake

Clean Fresh Air

Environmental Monitoring can provide an app driven air monitor, so you too can have mint cake fresh air

My name is Adrian Thiedeman, I live in Kendal in Cumbria. I have a background in applied chemistry, air & water pollution control and have spent the majority of my life providing monitoring solutions to consultants, universities, Government agencies and large manufacturers.

In the UK were are aiming to meet the WHO ( World Health Organisations) recommendations on fine particulate. Only today (21st of Feb 2020) The Government announced a ban on burning coal and certain logs on open fires and log burners.

We are constantly talking about traffic congestion and the pollution created by diesel vehicles, which includes fine particulate(pm10, pm2.5 and pm1) as well as Nitrogen Dioxide (NO2)

So what are we offering? Some organisation require very accurate professional monitoring equipment and testing services. Environmental Monitoring provide workplace exposure monitoring testing.

The type of organisations and people who want to know about their air quality ( pm10/pm2.5 and NO2) include Schools and colleges, nurseries, local authorities, fires services, public buildings, offices , architects, building engineers, facility managers

However many locations require a small unobtrusive device to run in the background and to provide a 24/7 outline into how good the air quality is, all on a neat easy to read app.

Environmental Monitoring provide a simple traffic light guide system or for an additional fee monthly reports. 01539 727878



Air You Sitting Comfortably ?

Please excuse the pun. Yes it is intended

Almost everyday we read about air pollution, we see pictures of buses and lorries pushing out large volumes of smoke and gas. We are then told about the need for electric car and the need to change our behaviour to slow down and stop climate change.

But what about in the home? Whilst we have constituents of outdoor road side pollution within our buildings we also have other items

  • Products of combustion from gas cookers ( gas and fine particulate)
  • Dust and gas from open fires and log burners
  • VOC’s from furniture, carpets and curtains

A recent report from the WHO suggested that certain potential hazards in the home required stricter guidelines, by monitoring indoor pollutants we can build a better picture of what we are surrounded by. This gives us the opportunity to regulate the flow of fresh air into our homes and to control the devices that contribute to poorer air quality

The 21st Century is here! and with it the amazing technology that allows us to talk to devise and control other systems. So as well as having you fridge talk to your phone to let you know how your tomatoes doing, or having your phone switch your lights on , you might want to use it to look around your house and get feel of the true quality of your environment.

Environmental Monitoring sell and hire a range of different indoor air quality monitoring systems and outdoor air quality systems. We can provide monthly reports and expert assistance. Please scroll down to view some data. This is the detailed professional version. We provide a simpler version which use a traffic light analogy i.e green, amber or red ( good, fair or poor air quality)

My name is Adrian Thiedeman. I have a background in applied chemistry, air and water pollution monitoring and have worked for a number of large consultants and test houses. Amongst our clients have been GSK, Rolls- Royce, Pepsi- Cola

please contact, 07799626406