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Outdoor Air Quality Monitoring of Particles

Ambient Air Monitoring

Ambient air monitoring may involve measuring particulate matter (PM) as well as particle number concentrations (PN), particle size distribution (PSD), or air sampling of particles for later analysis. Air quality monitoring efforts are usually driven by governmental regulation, but may also be motivated by a scientific interest or a neighborhood concern. These measurements are performed by researchers in industries or institutions, but they may also be performed by local advocacy groups. When combined with other information (such as weather data, or concentration of gaseous pollutants), air quality monitoring can give us a detailed picture of the quality of air we all breathe.

TSI is a leading global provider of particle measurement solutions that are easy to use, affordable, and highly accurate. Our research systems detect new particle formation down to 1 nm, and can measure particles as large as 20 µm, measuring in real-time. In the lab, on the road or for local air quality monitoring, long-term data relies on our performance.

Particle Number (PN) Concentration

Particle number measurements count all particles, regardless of size, offering insights into ambient air quality and the sources of pollutants. Tracking particle number concentrations (PN) helps assess the efficacy of control measures implemented by municipalities, industries, and other entities.

Ultrafine particles (UFPs) are a critical focus in environmental studies, with PN becoming a key metric globally. TSI Condensation Particle Counters (CPCs), trusted in both urban and remote environments, support this research. For example, the CPC 3750-CEN meets EN 16976 standards, measures up to 100,000 particles/cm³, and integrates seamlessly with monitoring networks, including ACTRIS in Europe and U.S. studies like MATES.

Particle Size Distribution (PSD)

Particle size distribution (PSD) offers key insights beyond particle number concentration, aiding researchers in understanding aerosol behavior in different environments. Knowing particle size is vital for studying respiratory health impacts, atmospheric transport, and source tracing, especially for ultrafine particles (UFPs) that significantly affect air quality and health.

Globally, researchers rely on Scanning Mobility Particle Sizers™ (SMPS™) to measure PSD in diverse settings, from urban areas to industrial sites. These instruments provide continuous, precise measurements down to 10 nanometers, making them essential tools in air quality networks and research for studying ultrafine particle dynamics.

Air Sampling

Since the measurement instruments are typically hosted inside a container or building, “sampling” means successfully transporting the particles from the ambient environment all the way to the measurement instruments’ inlets while imposing as little change as possible on the particles. Ensuring sample accuracy requires minimizing diffusion losses, drying the aerosol, and occasionally diluting the sample. TSI’s Sampling System for Atmospheric Particles 3750200 addresses these challenges with a PM10 sampling head and optional PM2.5 cyclone, a Nafion drier to reduce humidity, and a flow splitter for even sample distribution.

More Info for Beginners and Professionals

Which Pollutants are Most Important?

Air quality reflects the level of pollution in the ambient air, typically assessed by measuring one or more types of pollutants, broadly classified into gaseous and particulate categories. Common gaseous pollutants include ozone (O3), sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs). Particulate pollutants, on the other hand, can be addressed by their mass (PM10, PM2.5, PM1, 'ultrafines') and chemical characteristics (carbonaceous or non-carbonaceous), each impacting air quality distinctly.

Frequently asked questions

Q. How do monitoring networks/stations measure particles?

Traditional monitoring networks typically measure particles by assessing their mass concentration. This approach focuses on particle sizes like PM10, PM2.5, and PM1. Nowadays, networks include particle counters, particle sizers, optical instruments, and other tools to measure particle number concentration, particle size distribution, and sometimes particle composition.

Q. What particle sizes are usually monitored?

PM10 (≤10 µm) and PM2.5 (≤2.5 µm) are commonly tracked due to their health impacts. Ultrafine particles, also known as UFP, (<0.1 µm) are also studied for health relevance. ---> Click here to learn more about potential health effects of UFP

Q. What are ultrafine particles (UFPs)?

UFPs are particles with diameters less than 0.1 micrometers (100 nanometers), which can easily enter and affect the respiratory and cardiovascular systems.

Q. How are UFPs different from PM10 and PM2.5?

Unlike PM10 and PM2.5, which are measured by mass, UFPs are usually quantified by particle number concentration. This is because their small sizes means that they have too little mass to be detected using a mass-oriented measurement. Their small sizes also means that they can penetrate deep into the lungs and even enter the bloodstream, making them especially relevant in health-focused air quality studies. ---> Read more about the pros and cons of particle number- versus mass-based monitoring methods

Number- vs. Mass-Based UFP Monitoring Methods

Pros and Cons

Number- vs. Mass-Based UFP Monitoring Methods

Pros and Cons

Number-based UFP measurements reveal more particles than mass-based methods, highlighting health risks. Mass-based methods often miss UFPs, making number-based techniques crucial for accurate monitoring.

Read More