We recently hosted an incredible webinar with Thomas Grillo from Particles Plus about particle counting for indoor air quality (IAQ) investigation.

You can watch it here.

During the webinar, Thomas went over the following:

  • The basics of indoor air quality testing
  • Particles and their behaviour
  • Particle counters explained
  • Why use a particle counter
  • Types of particulate measuring devices and their applications in IAQ

Thomas also answered questions from the audience.

What affects the behaviour of a particle?

The human eye can see 40-micron size particles. Much of the particles that cause poor air quality are much smaller than what we can detect.

Standard particle counters measure from 0.3 to 10 microns.

  • Size: Settling rate is influenced by size, shape and density.
  • Gravity: Particles greater than five microns fall. Particles smaller than give microns tend to stay airborne and suspend for long periods of time.
  • Density: Affects suspension time.
  • Shape: Shape and surface area lends to longer suspension and lift.
  • Brownian Motion:Smaller, faster-moving molecules influence the direction and speed of motion of larger particles in a liquid or gas.

There are also environmental influences including:

  • airflow
  • ventilation
  • occupancy
  • thermal effects, and
  • shape and density of particulate.

The smaller a particulate is, the longer it will stay airborne in the respirable zone. Our activities also influence the levels of particulates indoors. For instance, dirt and soot brought in from shoes and clothes.

What is a particle counter? And how does it work?

A particle counter is an instrument or sensor that counts physical particles.

Particle counting is based on either light scattering, light obscuration or direct imaging.

A particle counter uses a high-intensity light source, like a laser, to illuminate particles as they pass through the detection chamber.

When a particle passes through the light source, a photodetector detects the redirected light. The photodetector sends the signal to a photo-amplifier that converts the signal into an actual count.

Why use a particle counter?

An indoor environmental professional cannot understand or evaluate indoor air quality without being able to quantify and qualify what is in the air.

While visual observation and olfactory input are very important tools, instrumentation and sample are key.

You should use a particle counter for indoor air quality testing to provide a quantitative analysis of airborne particulate for:

  • quality control of remediation process including cleanroom spaces, pharmacies and hospitals
  • regulatory requirements for public health and safety in offices for permissible exposure limits
  • limiting liability for those responsible for the air being breathed, and
  • air quality analysis for investigation, analysis and remediation.

Types of particulate measuring devices and their applications in IAQ:

Thomas highlights handheld and remote particle counters and the technology, pros and cons of two different types of particle counters including:

  • light blocking particle counters, and
  • light scattering particle counters.

Thomas covered a lot during this one-hour webinar and the question and answer period brought up a lot of great topics.

Watch this webinar if you want to learn more about how particle counters work and the best options on the market.

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Jonathan McCallum

Market Segment Manager: Occupational Health, Industrial Hygiene & Environmental Monitoring

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