Understanding Real-Time Particle Monitoring

Real-time particle monitoring measures the number and approximate size of airborne particles suspended in the air at a given moment.

Unlike laboratory analysis, which identifies the specific materials present, real-time monitoring provides immediate feedback about changing indoor air conditions during an inspection.

Because readings update continuously, the instrument allows us to observe how particle levels change from room to room and as conditions within the home change.

The monitor continuously measures airborne particles in two general size ranges.

Approximately 1 micron and larger

May include:

• Fine dust 
• Smoke 
• Some bacteria 
• Mold spores and fragments 
• Other microscopic airborne particles 

Approximately 5 microns and larger

May include:

• Pollen 
• Coarse dust 
• Fibers 
• Dust mite debris 
• Larger airborne particles 

The monitor measures particle size and quantity only.

It does not identify what the particles actually are.

Real-time monitoring allows us to observe changes that cannot be seen during a single laboratory sample.

During an inspection we may use it to:

• Compare particle levels between rooms 
• Observe changes as HVAC systems operate 
• Compare indoor and outdoor conditions 
• Identify areas with unusually elevated particle levels 
• Help determine whether additional investigation may be beneficial 

Because the readings update continuously, they often reveal patterns that would otherwise go unnoticed.

Real-time particle monitoring is an excellent investigative tool, but it has important limitations.

By itself, it cannot determine:

• Whether particles are mold, dust, pollen, or another material 
• The source of specific particles 
• Whether hidden mold is present 
• Whether a building is "safe" or "unsafe" 
• The cause of health symptoms 
• Whether remediation is necessary 

For these reasons, particle monitoring is interpreted alongside visual observations, moisture conditions, building history, occupant concerns, and, when appropriate, laboratory analysis.

Think of real-time particle monitoring as an early screening tool.

It tells us that something is changing, but not necessarily what is changing.

If elevated particle levels or unusual patterns are observed, laboratory analysis may be recommended to identify the materials present.

Laboratory analysis can identify many different particle types—including dust, fiberglass, pollen, cellulose fibers, soot, and many other materials—that cannot be distinguished by a particle counter alone.

Real-time particle monitoring measures how many airborne particles are present and how those levels change during an inspection. 

Laboratory analysis identifies what those particles actually are.

Neither method replaces the other. Real-time monitoring helps locate unusual conditions as they occur, while laboratory analysis provides detailed identification of the materials present.

Used together, they offer a more complete evaluation of indoor air quality.

Real-time monitoring is particularly useful when investigating:

• Persistent dust 
• HVAC-related concerns 
• Post-renovation conditions 
• Air movement between rooms 
• Unknown airborne particle sources 
• General indoor air quality concerns 

Interested in learning more?

• Indoor Air Quality Testing 
• Airborne Particles Guide 
• How We Approach Sampling