Fusarium spores — ~3–10 µm — mold common in water-damaged materials.

Chaetomium spores — ~3–8 µm — found in water-damaged drywall and cellulose.

Mucor / Rhizopus spores — ~3–20 µm — fast-growing molds in decaying organic matter.

Penicillium/Aspergillus fragments (sub-spore particles) — submicron to a few microns — allergenic and respirable.

Fungal hyphal fragments — variable, often submicron to several microns — can carry allergenic/mycotoxic components.

Dust mite allergens (fecal pellets & fragments) — ~10–40 µm (fragments smaller) — major indoor allergen source.

Cockroach allergens (Bla g proteins) — allergen particles often in 1–20 µm range — linked to asthma in urban settings.

Rodent (mouse/rat) urinary/fecal allergens — particle sizes vary; highly allergenic in infested buildings.

Gram-negative bacterial endotoxin (LPS on particulates) — bound to particles, respirable when aerosolized — inflammatory in lungs.

Mold mycotoxin-laden fragments — variable size — can be inhaled and cause irritation or immune effects.

Pollen grains (various trees/grasses/weeds) — ~10–100 µm — seasonal allergens that can infiltrate buildings.

Plant fungal spores (rusts, smuts) — ~2–30 µm — outdoor sources that enter indoors.

Animal dander (cat, dog) — fragments often 1–20 µm — persistent indoor allergen.

Feather and down particulates — variable; can carry allergens and microbes.

Human skin flakes / squames — ~10–40 µm (fragments smaller) — carrier particles for microbes and allergens.

SARS-like viral fragments (environmental RNA/protein debris) — submicron — can linger on aerosols or dust.

Environmental bioaerosol aggregates (mixed particles of dust + microbes) — variable sizes — common indoor exposure form.

Airborne protozoan cysts (rare indoors: e.g., Acanthamoeba cysts) — ~10–30 µm — generally outdoor/soil but possible in moist indoor niches.

Endotoxin-laden dust — particle-bound LPS from Gram-negative bacteria — triggers inflammation when inhaled.

Beta-glucan (fungal cell wall fragments) — particle-associated; inflammatory when aerosolized.

Inflammatory/oxidative particulates from cigarette smoke — submicron PM0.1–PM2.5 — carry adsorbed toxins and microbes.

Ultrafine combustion particles (cooking, candles, fireplaces) — <0.1–1.0 µm — deeply respirable and can carry biological matter.

Water-system aerosols containing microbes (e.g., from humidifiers, cooling towers) — variable sizes — Legionella and other opportunists can spread this way.

Viral-bearing droplet nuclei (dried aerosols after evaporation) — often submicron to a few microns — remain suspended and infectious longer.

Mixed indoor particulate matter (PM10 / PM2.5 / ultrafine PM0.1) — aggregate of dust, smoke, bioaerosols — central metric for indoor air health.

Rhinovirus — ~0.02–0.04 µm — a leading cause of the common cold; readily transmitted by aerosols.

Influenza virus — ~0.08–0.12 µm — seasonal flu viruses spread by droplets and aerosols.

Coronaviruses (e.g., SARS-CoV-2) — ~0.06–0.14 µm — spread via respiratory aerosols and droplets.

Respiratory Syncytial Virus (RSV) — ~0.15–0.2 µm — causes severe illness in infants and older adults.

Adenoviruses — ~0.07–0.09 µm — can cause respiratory, ocular, and gastrointestinal infections.

Measles virus (Rubeola) — ~0.1–0.2 µm — highly contagious airborne virus.

Varicella-zoster (Chickenpox) — ~0.12–0.2 µm — transmits via small airborne droplets.

Mumps virus — ~0.12–0.18 µm — spreads through respiratory secretions.

Enteroviruses (e.g., EV-D68) — ~0.03–0.05 µm — can be present in respiratory secretions.

Norovirus (aerosolized vomitus) — ~0.03–0.04 µm — primarily fecal-oral but can aerosolize during vomiting.

Mycobacterium tuberculosis (TB) — ~0.2–0.5 µm — airborne bacterial pathogen causing pulmonary TB.

Staphylococcus aureus (incl. MRSA strains) — ~0.5–1.0 µm — skin/respiratory colonizer that can spread via air on particulates.

Streptococcus pneumoniae — ~0.5–1.0 µm — common respiratory pathogen transmitted in droplets.

Legionella pneumophila — ~0.3–0.9 µm — transmitted by inhaling contaminated water aerosols (e.g., HVAC, showers).

Bordetella pertussis (whooping cough) — ~0.7–1.5 µm — spreads through respiratory droplets.

Chlamydia pneumoniae — ~0.3 µm (elementary body) — causes atypical pneumonia; transmits via aerosols.

Haemophilus influenzae — ~0.5–1.0 µm — respiratory pathogen spread in close quarters.

Pseudomonas aeruginosa — ~0.5–1.5 µm — opportunistic bacterium that can colonize wet building systems.

Klebsiella pneumoniae — ~0.5–1.5 µm — nosocomial respiratory pathogen.

Acinetobacter spp. — ~0.5–1.0 µm — environmental bacteria that can spread in healthcare settings.

Aspergillus spores (e.g., A. fumigatus) — ~2–5 µm — common mold in buildings, a risk for immunocompromised people.

Penicillium spores — ~2–5 µm — common indoor mold that can trigger allergies.

Cladosporium spores — ~3–10 µm — widespread indoor/outdoor mold and allergen source.

Alternaria spores — ~20–60 µm — outdoor/indoor mold linked to asthma and allergy.

Stachybotrys chartarum (black mold) spores — ~2–10 µm — associated with damp buildings and mycotoxin concerns.