TECHNICAL LIBRARY - AIR TREATMENT TECHNOLOGIES

HVAC Air Filter Efficiency: MERV, HEPA, and ULPA

Air filters are rated based on their ability to capture airborne particles of various sizes. The three main standards are:

MERV (Minimum Efficiency Reporting Value, 1-20) – Measures how well an HVAC filter captures particles from 0.3 to 10 microns. Higher MERV ratings indicate better filtration. Used in homes, offices, and industrial HVAC systems.
HEPA (High-Efficiency Particulate Air, 99.97% @ 0.3 microns) – Captures fine particles, including allergens, bacteria, and some viruses. Used in hospitals, laboratories, and clean environments.
ULPA (Ultra-Low Penetration Air, 99.999% @ 0.1 microns) – Provides the highest filtration efficiency for ultra-fine particles. Used in cleanrooms, pharmaceutical production, and specialized medical applications.

UV Germicidal Irradiation Dosage Table

Ultraviolet (UV) germicidal irradiation is an effective method for inactivating microorganisms by disrupting their DNA or RNA, preventing replication.
The required UV dosage depends on several factors, including the type of microorganism, exposure time, airflow, humidity, and temperature.
This table provides the incident energy levels of germicidal UV radiation at 253.7 nanometers (nm) necessary to achieve microbial inactivation. Dosage is expressed in microwatts per square centimeter per second (μW/cm²/sec), and the values listed indicate the energy required for 90% inactivation (D90) and complete destruction of various microorganisms.
Understanding these dosage requirements is essential for designing effective UV disinfection systems in HVAC applications, healthcare settings, water treatment, and other environments requiring high-level sanitation.