Indoor PM10 Testing: What Coarse Particles Are Doing to Your Airways

What Is PM10?

PM10 refers to particulate matter 10 micrometers or smaller in diameter — roughly one-seventh the width of a human hair. This size class is often called coarse particulate matter, and it encompasses a wide range of airborne material: house dust, pet dander, pollen grains, mold spores, some bacterial clusters, textile fibers, and soil particles tracked indoors. Because these particles are larger than fine PM2.5, they don't penetrate as deeply into lung tissue — but that doesn't make them harmless.

When inhaled, PM10 particles are largely deposited in the upper airways: the nose, throat, and bronchi. The mucous membranes lining these passages act as a first line of defense, trapping particles and triggering immune responses. Repeated or prolonged exposure overwhelms those defenses, producing the nasal inflammation, irritation, and respiratory symptoms that many Portland and Seattle residents attribute to seasonal allergies — when the real culprit may be the air inside their own homes.

Illumenair measures PM10 concentrations in micrograms per cubic meter (µg/m³) using advanced real-time particle analysis. Because levels vary dramatically from room to room — a carpeted bedroom with a sleeping dog will read very differently from a tiled kitchen — our assessments capture data in each occupied space rather than relying on a single-point sample.

PM10 Health Effects: More Than Sneezing

The health effects of PM10 exposure span from mild upper-airway irritation to serious, chronic respiratory disease. Because PM10 includes many of the particles people are most commonly allergic to — dust mite debris, pet dander, pollen, and mold spores — even moderate indoor concentrations can trigger significant immune responses in sensitive individuals. The World Health Organization links every 10 µg/m³ increase in PM10 exposure to a 4% increase in respiratory mortality, underscoring that coarse particles carry real long-term risk.

Certain populations face heightened risk: children whose airways are still developing, older adults with reduced lung reserve, and anyone already living with asthma or COPD. For these groups, indoor PM10 is often the difference between a controlled condition and a recurring flare.

Common Indoor Sources of Coarse Particulate Matter

Unlike outdoor PM10 — which is dominated by vehicle emissions and industrial sources — indoor PM10 is generated by the people, animals, and activities inside a building. Understanding where particles originate is the first step toward reducing them.

• House dust and settled particles. General household dust is a composite of skin cells, textile fibers, dust mite debris, and tracked-in soil. It accumulates on surfaces and re-enters the air every time occupants move through a space.
• Pet dander. Cats, dogs, and other animals shed microscopic skin flakes continuously. Pet dander is a primary PM10 allergen and can remain airborne for hours, accumulating to high concentrations in rooms where pets sleep.
• Pollen. Outdoor pollen enters through open windows and doors, settles on clothing and shoes, and is redistributed indoors. In the Pacific Northwest, tree pollen season can significantly elevate indoor PM10 in poorly sealed homes.
• Mold spores. Mold colonies release spores in the PM10 size range. High-humidity areas — bathrooms, crawl spaces, laundry rooms — are common sources, but mold can colonize any surface with adequate moisture.
• Vacuuming and sweeping. These activities are meant to remove particles, but without a high-efficiency filter, they resuspend settled dust and dander into the breathing zone. PM10 spikes during and immediately after cleaning are measurable and clinically relevant.
• Cooking. Frying, grilling, and high-heat cooking generate coarse particles alongside fine ones. Without adequate ventilation, kitchen PM10 levels can spike dramatically during meal preparation.
• Renovation and construction dust. Sanding, cutting drywall, and demolition release large quantities of coarse particles. Construction dust from nearby outdoor projects also infiltrates through gaps and HVAC systems.
• Textile fibers. Carpets, rugs, upholstered furniture, and bedding shed fibers continuously. These materials also trap and re-release particles that settle into them, acting as reservoirs rather than sinks.

Why Indoor PM10 Testing Matters

Dust particle testing for indoor air isn't about finding visible dirt — it's about quantifying the invisible particle load that occupants are breathing every day. Indoor PM10 levels routinely run two to three times higher than outdoor concentrations because human activity continuously generates and resuspends particles in an enclosed space. Opening a window doesn't fix this; in fact, it can introduce outdoor pollen and combustion particles on top of what's already present.

Room-by-room data reveals patterns that a single-sensor approach misses entirely. A bedroom with wall-to-wall carpet and a pet that sleeps at the foot of the bed may read at three times the concentration of a tiled entryway two rooms away. That's eight hours of elevated PM10 exposure every night — precisely when the body is trying to recover. Identifying that room as the problem space is the actionable intelligence homeowners and clinicians need.

Illumenair's professional-grade testing system also allows comparison between quiescent conditions (undisturbed air) and resuspension conditions (after normal activity like walking across carpet or making the bed). This comparison reveals how much particulate matter is stored in surfaces and furnishings — and how much of it becomes airborne with routine movement. For patients with allergic rhinitis, asthma, or COPD, this data directly informs treatment and remediation decisions.

Learn more about how Illumenair conducts assessments and what same-day results look like in practice.