At the Bernhard Nochter Institute for Tropical Medicine in Hamburg, Germany, scientists are studying the deadly Ebola virus in a P4 laboratory. The laboratory air is forcibly exchanged more than 20 times per hour, and all exhaust gases must pass through an invisible physical barrier—HEPA filters —before being released into the atmosphere. This is a microcosm of biosafety laboratories worldwide.
Protection Levels under Global Standards
According to the standards of the U.S. Centers for Disease Control and Prevention (CDC), protection levels are classified from low to high as Biosafety Level 1 to Level 4.
Different laboratory levels correspond to different levels of pathogen risk:
BSL-1/P1: Handles microorganisms known not to cause disease in healthy adults, such as non-pathogenic Escherichia coli.
BSL-2/P2: Handles pathogens with moderate potential harm to humans, such as seasonal influenza and hepatitis viruses. Laboratories require restricted access and the use of biosafety cabinets in procedures that may generate aerosols.
BSL-3/P3: Handling pathogens that can be transmitted via aerosols and can cause serious or even fatal illnesses, such as Mycobacterium tuberculosis and SARS coronavirus.
BSL-4/P4: Handling dangerous pathogens that can be transmitted via aerosols, are highly pathogenic, and generally have no effective vaccines or treatments, such as Ebola virus.
Core Sources of Risk in Laboratories
One of the greatest threats to laboratories is “aerosols“—small solid or liquid particles suspended in the air.
Many dangerous pathogens are transmitted through this route. Therefore, routine procedures such as opening lids, pipetting, and centrifugation can generate pathogen-containing aerosols, becoming potential sources of leakage. As of 1999, more than 5,000 accidental laboratory infections had been recorded worldwide, resulting in 190 deaths. This highlights the extreme importance of establishing reliable physical barriers and strict operating procedures in laboratory environments where exposure to dangerous pathogens occurs.
The Ultimate Guardians of Laboratory Air: HEPA and ULPA Filters
HEPA (High-Efficiency Particulate Air) filters are one of the key hardware barriers protecting laboratory personnel and the external environment.
The working principle of these filters is not a simple sieving effect, but relies on three intricate physical mechanisms: inertial impaction, interception effect, and diffusion effect. Notably, for particles smaller than 0.3 micrometers (such as most viruses), HEPA filters are actually more efficient due to the diffusion effect. This means that HEPA filters are equally effective against many viruses.
A More Stringent Choice:ULPA Filters
When the efficiency of standard HEPA filters is insufficient, ULPA (Ultra-High-Efficiency Particulate Air) filters come into play, serving as the preferred choice for environments requiring extreme cleanliness, such as the highest-level biosafety laboratories, cutting-edge semiconductor production lines, or certain surgical environments.
A Comprehensive Laboratory Protection System
The safety of high-level biosafety laboratories does not rely solely on a single HEPA or ULPA filter, but rather on a complex system combining “hard power” and “soft power.”
Hard power includes a negative pressure environment, directional airflow, airtight structure, and a high-efficiency filtration system. For example, the core area of a P3 laboratory is typically maintained under negative pressure, with forced air exchange dozens of times per hour to ensure that airflow only moves from clean areas to potentially contaminated areas. All exhaust air must be treated by high-efficiency particulate air (HEPA) filters.
Soft power, on the other hand, is a rigorous management system, which is even more important than hardware. This includes: strict risk assessment, comprehensive personnel training and supervision, and continuous safety monitoring.
From the standard laboratories of the U.S. Centers for Disease Control and Prevention (CDC) to the Jean Mérieux Laboratory in Lyon, France, and the Institute for Tropical Medicine in Hamburg, Germany, high-level biosafety laboratories worldwide constitute the first line of defense against the most dangerous pathogens. HEPA/ULPA filters act as the final “gatekeepers,” effectively trapping dangerous aerosol particles within the system. Follow Trenntech for customized HEPA/ULPA filters for your laboratory, explore the mysteries of life, and defend against disease threats.