| Mask Type | Likelihood of Stopping You Getting Infected | Likelihood of Stopping You Transmitting | Notes | |-----------------------|------------------------------------------------|---------------------------------------------|-------------------------------------------------------------------------------------------------| | Cloth Mask | Low to Moderate (20–50%) | Moderate (50–70%) | Can block larger droplets but has low filtration efficiency for aerosols. | | Surgical Mask | Moderate (60–80%) | High (80–90%) | Effective at blocking large droplets; moderate protection from aerosols. | | N95 Respirator | High (95–99%) | Very High (95–99%) | Superior filtration for both droplets and aerosols; depends on proper fit and seal. | - lower dose exposure lowers severity and increases chance of being under [[infectious dose]] - reduces contact transmission from touching face - captures or reduces spread of respiratory emissions feet -> inches #### Respiratory Emissions | Category | Size Range | Behavior | Examples | | | -------------- | -------------- | ----------------------------------------------------------- | ----------------------------- | ---------------------------------------------------------------------------------- | | Large Droplets | 5–100+ microns | Fall quickly (3–6 feet), land on surfaces or mucosal areas. | Sneezing, coughing. | Typically carry higher concentrations of pathogens and settle quickly on surfaces. | | Small Droplets | 5–20 microns | Can evaporate into aerosols under certain conditions. | Speaking, breathing. | Can evaporate into droplet nuclei, remaining suspended as aerosols. | | Aerosols | <5 microns | Remain airborne for hours, travel over long distances. | Fine aerosols in exhaled air. | Can travel deeper into the respiratory tract and remain airborne for hours. | #### ASTM Mask Level Standards Table | ASTM Level | Barrier Protection | Bacterial Filtration Efficiency (≥3 microns) | Particulate Filtration Efficiency (≥0.1 microns) | Fluid Resistance (mmHg) | Differential Pressure (Delta P) | Applications | | ---------- | ------------------ | -------------------------------------------- | ------------------------------------------------ | ----------------------- | ------------------------------- | ------------------------------------------------------------------------------------------------------ | | Level 1 | Low Barrier | ≥95% | ≥95% | 80 mmHg | <5.0 mm H₂O/cm² | General use, low-risk situations (e.g., basic procedures, patient exams). | | Level 2 | Moderate Barrier | ≥98% | ≥98% | 120 mmHg | <6.0 mm H₂O/cm² | Moderate-risk environments (e.g., surgical procedures, where moderate exposure to fluids is possible). | | Level 3 | High Barrier | ≥98% | ≥98% | 160 mmHg | <6.0 mm H₂O/cm² | High-risk environments (e.g., surgeries, heavy fluid exposure, or high-pressure splashes). | - Fluid Resistance: The mask's ability to prevent fluid penetration at different pressures (measured in mmHg). - Differential Pressure (Delta P): Indicates the mask's breathability; higher pressure means more resistance, which can reduce comfort. #### Protects Against Several [[means of infection transmission]] - respiratory emissions (droplets, aerosols) - bloodborne pathogens (splashes of blood or bodily fluids) - environmental particles (dust, pollen, smoke, or other fine particulates) - chemical irritants (some masks, non-oil-based chemical particles) - allergens (pet dander, mold spores) #### Common Airborne Pathogens and Their Properties | Disease(s) | Type | Transmissibility | Duration/Proximity Needed | Virus Viability | Infectious Dose | Health Risk | Viral Load | Special Properties | | ----------------------------- | -------- | ---------------- | ------------------------------------------------- | ----------------------------------------------------- | ----------------------------- | --------------------------------------- | --------------- | ------------------------------------------------------------------------------------------------------------- | | Measles | Virus | Extremely High | Brief exposure at a distance | Hours in air, stable in aerosols | 1–10 viral particles | Severe (especially in children) | High | Highly contagious; aerosols remain infectious in the air for up to 2 hours. | | Tuberculosis | Bacteria | High | Prolonged close exposure | Hours to days in aerosols | 1–10 bacteria | High; chronic respiratory illness | Low to Moderate | Aerosols can remain infectious for hours; causes latent infections in some cases. | | COVID-19 | Virus | High | Prolonged close exposure or aerosol-rich settings | Hours to days on surfaces; moderate aerosol stability | Estimated 100–1,000 particles | Moderate to Severe (varies by person) | Variable | Can spread via droplets and aerosols; asymptomatic carriers increase transmission risk. | | Influenza (Flu) | Virus | Moderate to High | Close contact for several minutes | Hours in droplets and on surfaces | 10–100 viral particles | Moderate; severe in vulnerable groups | Moderate | Seasonal variability; capable of antigenic drift and shift, leading to new strains. | | Chickenpox, Shingles | Virus | High | Brief exposure at close proximity | Hours in aerosols | <10 viral particles | Mild to Severe (severe in adults) | High | Can spread before symptoms appear; aerosols and direct contact with lesions. | | Whooping Cough | Bacteria | Moderate | Close contact, prolonged exposure | Hours on surfaces; low aerosol stability | ~10 bacteria | Moderate to Severe | Moderate | Primarily affects children; spreads via droplets, but smaller particles may aerosolize. | | Common Cold | Virus | Moderate | Close contact for several minutes | Hours to days on surfaces | ~100 viral particles | Mild | Moderate | Causes widespread mild infections; primarily droplet but can be aerosolized. | | Legionnaires’ Disease | Bacteria | Low | Prolonged exposure to contaminated water systems | Stable in waterborne aerosols | ~1,000 bacteria | Severe in immunocompromised individuals | Low | Spread through contaminated water aerosols (e.g., air conditioning systems); not person-to-person. | | Histoplasmosis | Fungus | Low | Prolonged exposure to contaminated environments | Weeks to months in soil | ~100 fungal spores | Severe in immunocompromised individuals | Low | Spores aerosolized from bird or bat droppings; prevalent in specific geographic regions (e.g., Midwest U.S.). | | Hantavirus Pulmonary Syndrome | Virus | Low | Prolonged exposure to rodent droppings | Stable for days in contaminated environments | ~100–300 viral particles | High; often fatal | Moderate | Aerosolized from rodent urine, droppings, or saliva; not transmitted person-to-person. | - Transmissibility: How easily the pathogen spreads in typical conditions (airborne, aerosolized, or droplet). - Low: Requires specific environmental conditions or direct contact. - Moderate: Requires close contact or prolonged exposure. - High: Spreads easily with minimal exposure. - Extremely High: Among the most contagious diseases known (e.g., Measles). - Infectious Dose: The approximate number of particles or organisms needed to establish an infection. Lower doses generally indicate higher risk of infection. - Health Risk: Indicates how severe the disease is, with factors such as fatality rates, complications, and population vulnerability considered. - Special Properties: Unique factors influencing transmission or infection, such as persistence in the air, pre-symptomatic spread, or environmental reservoirs. - Virus Viability: How long the pathogen remains infectious in aerosols or on surfaces. - Viral Load: The concentration of infectious particles in respiratory emissions, which affects infectious dose and severity.