Indoor air contains thousands of microscopic particles. Most are completely normal and are simply part of everyday life. Others may indicate moisture problems, construction dust, HVAC issues, or outdoor contaminants entering the home.

When laboratory particle identification is performed, each particle is examined under a microscope and categorized based on its physical characteristics.

This guide explains many of the materials that may appear in an indoor air quality laboratory report.

Finding particles in indoor air does not automatically indicate a problem.

Every home contains a mixture of particles from people, pets, clothing, outdoor air, construction materials, and normal household activities.

The goal of laboratory analysis is not to eliminate every particle—it is to determine whether the types and amounts present appear typical or suggest an unusual source that deserves further investigation.

Naturally shed by people and pets. Usually one of the most common indoor particles.

Human and animal hair fragments are common in occupied buildings.

Microscopic debris produced by dust mites. Common in bedding, upholstery, and carpeting.

A mixture of fibers, organic material, minerals, and microscopic debris that accumulates through everyday living.

Usually originate from paper products, wood products, insulation, or natural fabrics.

Often released from clothing, towels, bedding, and upholstery.

Typically come from carpeting, clothing, furniture, and household textiles.

May originate from insulation, HVAC duct liners, or fiberglass building products.

Fine gypsum particles may appear after remodeling, repairs, or construction work.

Produced during woodworking, sanding, flooring installation, or general wear.

Can occasionally be found from insulation products, windows, or manufacturing materials.

Often enters from outdoors or is generated from concrete, masonry, brick, or stone materials.

Seasonal pollen enters homes through open doors, windows, ventilation systems, and clothing.

Small pieces of leaves, wood, bark, or other vegetation commonly enter from outdoors.

Microscopic pieces from insects are commonly found in both indoor and outdoor environments.

May originate from fireplaces, candles, cooking, tobacco smoke, vehicle exhaust, or fire damage.

Often associated with outdoor burning, fireplaces, or wildfire smoke.

Microscopic particles from painted surfaces or renovation activities.

Small amounts of aluminum, iron, or other metals may be present from building materials, machinery, or outdoor sources.

Common in coastal environments like Charleston, where airborne sea spray can contribute small salt particles.

Laboratory specialists examine:

• Particle size 
• Shape 
• Color 
• Surface texture 
• Optical characteristics 
• Material composition 

These characteristics help determine the most likely source of each particle.

Particle identification is a valuable tool, but it has limits.

By itself, laboratory analysis cannot determine:

• Whether a particle is causing health symptoms 
• When the particle entered the home 
• The exact source without additional investigation 
• Whether remediation is necessary 

Instead, results are interpreted alongside the inspection findings, the condition of the home, and any additional testing that was performed.

You may also be interested in:

• Indoor Air Quality Testing 
• Particle Monitoring 
• Sample IAQ Laboratory Report 
• How We Approach Sampling