Biosafety Level 4

The scientific research about various exotic and highly infectious pathogens has increased exponentially in recent years. These pathogens are contemplated to be bio-weapons in the making. These pathogens are classified based on risk and priority by the Centre for Disease Control and Prevention (CDC) as bioterrorism. The biosafety regulations and strategies have to be followed strictly to work with unique microorganisms in the US. These research laboratories need Biosafety level-2 (BSL-2), Biosafety level-3 (BSL-3), or Biosafety level-4 (BSL-4) containment that is sketched in Biosafety in Microbiological and Biomedical Laboratories (BMBL).  Research in BSL-4 labs needs a lot of precautions, highly strict training, and powerful infrastructure.

What is Biosafety Level-4?

Biosafety level-4 is designed to be the highest level of biosafety. These laboratories are suitable for working with microorganisms that can be transmitted through aerosols. These microbes are capable of causing grave diseases that could lead to human death. Moreover, in BSL-4 labs microbes with no available vaccines and treatment are handled. BSL-4 labs are strictly restricted and only allow trained individuals. Every person that enters the laboratory is recorded carefully. The waste from a BSL-4 lab such as air, water or trash must also be sanitised before leaving the infrastructure. These laboratories must be placed away from traffic. The main entrance of the BSL-4 lab is hooked with airlocks to reduce the potential that the aerosols from the lab are eradicated. 

Diagnostic and research work related to easily communicable pathogens are looked after here in BSL-4 labs. These pathogens are fatal to humans. Ebola, Nipah, and Marburg viruses are a few names of pathogens that have been handled in BSL-4 laboratories.  Organisms that are closely related to deadly pathogens and pathogens that are poorly characterised are also handled here. They remain in BSL-4 until more information about these organisms is obtained.

Biosafety Level-4 labs (Types) 

There are two major types of BSL-4 laboratories. They are-Cabinet laboratories and Protective-suit laboratories. 

• Cabinet Laboratories

In these labs, all research and experimentation work strictly has to be done in a class III biosafety level cabinet. Every substance that leaves the cabinet must be sanitised before leaving the cabinet. This is achieved by passing the substances through an autoclave or using a disinfectant tank. These labs have unique custom made gloves boxes that are connected in long lines. The cabinets are strictly required to be fitted with seamless edges for cleaning effectively.

• Protective-suit labs

All the experimentation work strictly has to be done in a class II biosafety level cabinet. The people working in this lab must wear a positive pressure suit. The personnel must also wear breathing air hoses.

For leaving a BSL-4 lab, every person strictly has to pass through a chemical shower for sanitisation. After sanitisation, they can remove their positive pressure suits, along with taking a personal shower.

Additional protection for BSL-4

The following section elucidates the unique systems for the protection of BSL-4 labs.

• Control of pressure-driven airflow 

This is a primary safety measure that uses negative pressure. This causes the air to route from the safe zones to hazard zones. Any leaks that may develop will draw fresh air into the lab; this is possible due to negative pressure in the lab. This makes sure the contaminated air does not leave the facility. 

A bladder valve is used as a ventilation VAV box. These valves are operated linearly and are highly reliable. 

An example that has this type of facility is the Canadian Science Centre for Human and Animal health. It is the only infrastructure that works at high biosafety levels for humans and animals. 

• Bio-sealed doors and dampers

There are two types of unique bio-seal doors. They are mostly used at the entrance of BSL-4 buildings. The first type is called the submarine door. It has a turning wheel and a mechanical clamp that shuts the door. The other type of bio-seal consists of a pressurised bladder that seals the door after it is shut. 

Bio-seal dampers function is to isolate ducts at the exit of the BSL-4 lab building. They automatically seal the laboratory once the sensors indicate negative pressure. They also aid in isolating High-efficiency particulate air (HEPA) filters during decontamination. 

• Building pressure sensors

This is a key technology to protect the BSL-4 buildings from bioterrorism. It also needed to build biocontamination labs for measuring the pressure of the building outside. This is because the outside pressure gives a common reference pressure point that can be used to control negative pressure levels in the lab. This technology uses one or more wind shielded sensors on a 20-ft long pole that is placed on the roof of the building. Nowadays, these sensors are placed on every floor to get accurate information.

• Ventilation and filtration 

The BSL-4 labs are provided with 100 per-cent outside but with no air returned. All the exhaust air from the lab is passed through double HEPA filters.The filters are High Efficiency Particulate Absorbing filters that effectively rid the air of most particulate matter. They are arranged in a series manner. The supplied air from the outside is passed through a single HEPA filter. These filters are placed on the maintenance floors that are above the BSL-4 labs. This allows easy maintenance of the filters.

Facilities 

Various BSL-4 labs around the world are listed here. 

Conclusion  

The article focused on the biosafety level-4. It is the highest biosafety level. Research in BSL-4 labs needs a lot of precautions, highly strict training, and a powerful infrastructure. These laboratories are suitable for working with microorganisms that can be transmitted through aerosols. Ebola, Nipah, and Marburg viruses are a few names of pathogens that have been handled in BSL-4 laboratories. The unique systems for the protection of BSL-4 labs are-control of pressure-driven airflow, bio-sealed doors and dampers, building pressure sensors, and ventilation and filtration. The names of a few BSL-4 labs are The National Institute of Virology in Pune, The High-Security Animal Disease Laboratory in Bhopal, and The Robert Koch Institute in Berlin.