urban air quality thumbnail image

Urban Air Quality – The Role and Importance of Monitoring VOCs

The World Health Organisation estimates poor urban air quality accounts for 7 million deaths per year. Unless poor air quality can be addressed death rates will continue to rise.
Download Guide

Back to Industry Guides

Photochemical and sulphurous smog differ not only in composition but also on the weather conditions that give rise to them. Photochemical smog occurs in hot sunny conditions, and peaks in the afternoon. Sulphurous smog is worse in cold damp atmospheres, peaking at dawn. Pollution may also be carried in the wind into a city, most notably smoke caused by the burning of vegetation, and from power station emissions.

Clean Air

Our atmosphere is dynamic. Biological, physical and chemical processes contribute to ‘clean air’, a gas mix which is remarkably well balanced for life and free of toxic gases and particulates. With the exception of halocarbons and a few inert gases, the concentration of gases in the atmosphere are in constant flux, and are dynamically mediated by living processes. Moreover, they are often at an optimal level for life. Oxygen is balanced at a concentration that enables aerobic organisms such as us to breath easily, whilst not so high as to cause unquenchable forest fires. Carbon dioxide is plentiful enough for plants to grow, both as a source of carbon and in retaining sufficient but not too much warmth from the sun. Elements essential for life such as sulphur and iodine are transported from land to sea in the form of volatile organic compounds (VOCs).

Many gases, which are toxic or harmful to life are removed by chemical and physical adsorption on solid particles (particulates) which ultimately fall out of the air under gravity as dust or rain. What is more, through a series of chemical reactions, including reactions with sunlight (photochemical reactions), the atmosphere is kept almost completely free of specific VOCs released by plants, it would seem to their own and wider advantage. For example, it has been recently established that on being bruised, leaves release VOC messengers (pheromones) that attract predators of leaf eating insects!

acid rain on plants

Photochemical smog is a major environmental pollution culprit, produced when sunlight reacts with nitrogen oxides (NOX) and at least one volatile organic compound (VOC) in the atmosphere.

Human Impact on Air Quality

Gases and particulates arising from human activity face exactly the same processes as those realised naturally: being either photochemically oxidised and-or in forming and condensing on particulates which ultimately fall out as dust or rain. However, the sheer volume of certain ‘primary pollutants’ discharged by human activity can be hazardous, as well as in generating ‘secondary pollutants’ through various reactions. Also, high concentrations of VOCs, for example, when released into the air, may ‘overwhelm’ the very low concentrations of highly reactive atmospheric cleansing agents in air, such as OH and NO3 allowing them to remain unchanged for longer times than they would be in cleaner air.

Primary pollutants, released directly into the atmosphere, include:

  • NO and NO2 (‘NOx’), chiefly from vehicle exhaust and coal fired power stations.
  • SO2 and SO3 (‘SOx’) primarily from sulphurous coal burning stoves and power stations.
  • CO from vehicle exhaust, wood and coal burning.
  • VOCs apart from methane from the following sources:
    Unburnt hydrocarbons from vehicles. This pollutant is eliminated where legislation ensures catalytic conversion of unburnt hydrocarbons.
    Solvent release and spills. These may arise from poorly controlled industrial plant process, fugitive emissions and spillages, but also a feature of urban pollution due to volatilisation of
    solvents in domestic products such as cleaners and polishes.
    Terpenes from forest fires.

Secondary pollutants, resulting from action of sunlight on NOx and VOCs, are:

  • Ozone, O3, which in the lower atmosphere is very harmful to all lifeforms.
  • Aldehydes such as formaldehyde, a harmful biocide.
  • Peroxyacyl nitrates (PANs).urban air quality
  • A resultant photochemical or ‘Los Angeles’ smog comprising particulates often containing metal oxides, nitric acid, PAN, dissolved VOC’s and SVOC’s.
  • Sulfurous or ‘London’ smog, formed from sulfurous coal burning, comprising water, ash, PAH’s, sulfuric acid and nitric acid.
  • Acid rain is a secondary pollutant, formed by reaction of rain droplets with NOx and SOx.
Download Guide

Download Our FREE Guide

“Urban Air Quality – The Role and Importance of Monitoring VOCs”

Urban air pollution is linked with increased levels of stroke, heart disease, lung cancer and chronic respiratory diseases. The world health organisation estimates poor urban air quality accounts for 7 million deaths per year. Currently half of the world’s population live in urban areas and 1.5 million people are added to the global urban population every week. Unless poor air quality can be addressed death rates will continue to rise.

urban air quality sensor guide

Download Guide

Monitoring VOCs of Urban Air Quality

10.0 eV VOC Gas Sensor

Range: 0 to >100 ppm. Minimum detection limit: 5 ppb. 10.0 eV lamp. The 10.0 eV VOC gas sensor - MiniPID 2 is used for enhanced selectivity of compounds with lower ionisation energies.

Product Details
11.7 eV VOC Gas Sensor

Range: 0 to >100 ppm. Minimum detection limit: 100 ppb. 11.7 eV lamp. The 11.7 eV VOC gas sensor lamp extends the range of detectable compounds, only available from ION Science.

Product Details
High Sensitivity VOC Gas Sensor

Range: 0 to 3 ppm. Minimum detection limit: 0.5 ppb. 10.6 eV lamp. The high sensitivity VOC gas sensor, is the highest sensitivity VOC gas sensor for sub PPB level detection.

Product Details
PPB VOC Gas Sensor

Range: 0 to >40 ppm. Minimum detection limit: 1 ppb. 10.6 eV lamp. The PPB VOC gas sensor - MiniPID 2 is optimised to deliver an exceptionally low background which allows for optimum low-end sensitivity.

Product Details
PPB WR VOC Gas Sensor

Range: >200 ppm. Minimum detection limit: 20 ppb. The MiniPID 2 PPB Wide Range VOC gas sensor is optimised to deliver an exceptionally low background which allows for optimum low-end sensitivity.

Product Details
PPM VOC Gas Sensor

Range: 0 to 4000 ppm. Minimum detection limit: 100 ppb. 10.6 eV lamp. The PPM VOC gas sensor - MiniPID 2 is designed for detecting VOCs over the widest dynamic range on the market without compromising performance.

Product Details
PPM WR VOC Gas Sensor

Range: >10,000 ppm. Minimum detection limit: 500 ppb. 10.6 eV lamp. The MiniPID PPM WR VOC gas sensor is designed for detecting VOCs over the widest dynamic range on the market without compromising performance.

Product Details
Sensor Development Kit (SDK)

Sensor Development Kit (SDK) for the integration of the MiniPID 2 photoionisation sensor.

Product Details

Download your FREE Guide

Simply complete the form below to obtain your FREE Guide on ‘Urban Air Quality – The Role and Importance of Monitoring VOCs.

Related Guides

Aromatic Gases – What Are They?

Aromatic gases contain at least one aromatic ring of which benzene is the simplest form. Benzene itself forms the well know group of compounds (BTEX).

View Details

Benzene Detection – Fixed Instruments

Benzene Detection (Fixed Instruments) - ION Science's Fixed Photoionisation Detectors protect workers and the public from benzene exposure

View Details

Fenceline Monitoring

Hazardous air pollutants are those known to cause cancer and other serious health impacts. This is why fenceline monitoring is important!

View Details

Fugitive Emissions Monitoring

Gas leak equipment reduces the likelihood of leaks and the best way to reduce fugitive emissions is through regular leak testing and maintenance.

View Details

Gas Detection Equipment – Choosing The Right Type

Knowing which is the best gas detection equipment when so many are available within the market, yet they all seem to do the same job until close inspection.

View Details

Gas Detection Instrument – Do you Require One In Your Industry?

The Gas detection Instrument guide will help you understand the requirement for each type of instrument and which will be best suited to your industry.

View Details

Gas Detection System – PID Or FID?

Gas Detection System, the main differences and benefits of using photoionisation detection and flame detection when monitoring fugitive emissions.

View Details

Monitoring Aromatic Gases

Monitoring aromatic gases early is crucial to limit the effects on worker’s health. This all depends upon how much they are exposed to and for how long.

View Details

Occupational Exposure To Toxic Chemicals

Understanding an Occupational Exposure to toxic chemicals on a daily basics when working within the Oil & Gas industry.

View Details