A hood in laboratories are an effective means of capturing flammable, irritant, corrosive, carcinogenic vapors, etc. to prevent personnel exposures and avoid their dissemination in the laboratory atmosphere. When the hatch is down, the cab is also a physical barrier that protects the operator from hazards such as splashes, aerosols, fires, and minor explosions.

Fume hoods are a type of ventilation system with the primary function of protecting the user against exposure to chemical vapors, gases, dust, and aerosols. They function as physical barriers between reagents and the laboratory, offering protection against inhalations, spills of hazardous substances and fire.

A typical hood has a box-shaped structure with a movable window. The experiments are carried out inside the hood that is ventilated constantly and safely, usually by means of ducts. Chemical vapors are extracted and diluted many times in the atmosphere rendering them harmless to human health. If there are environmental concerns, a treated exhaust system can be installed to remove most of the vapors from the outside air stream.

It works by maintaining negative air pressures inside the cabin and preventing any air particles from escaping to the outside. The speed at which the air enters the hood is very important to guarantee the safety of the equipment. High speeds can create turbulence that will allow the air inside to escape, but low speeds may not be enough containment.

Biological safety cabinets are ventilated rooms designed to limit the risk of laboratory personnel exposed to infectious agents as much as possible. This is especially important considering that many of the operations carried out in a laboratory involve the formation of aerosols. The main objective of this equipment is to provide a work area that minimizes the probability that an airborne particle has to escape to the outside of the cabin and thus contaminate the operator and the area around him. In addition, some of them offer protection to the material that is handled.

When a biological safety cabinet is used by properly trained personnel aware of its limitations, it becomes a very effective containment equipment to reduce the possible escape of biological contamination. However, it is important to bear in mind that a cabin is never a substitute for a proper microbiological technique.

These cabins have two systems that prevent contamination from escaping: air barriers and filters. Air barriers are created by allowing air to flow in only one direction and at a constant speed, creating a true “curtain” of air known as laminar airflow. It is, by definition, a flow with no turbulence. The purpose of the filters is to trap the particles contained in this air flow and the most commonly used are HEPA filters, which retain particles up to 0.3 microns in diameter with an efficiency of 99.97%.