The purpose of safety ventilation is to eliminate airborn harmful substances. In most case these substances are neither visible nor smell. It is recommended to observe particular caution. Since the health risks are significant in laboratory work, good and reliable protection ventilation is crucial for the staff.

The purpose of protection ventilation is to eliminate harmful substances in the air that we breathe. These substances are neither visible nor smell in many cases. It is recommended to observe particular caution. Since the health risks are significant in laboratory work, good and reliable protection ventilation is crucial for the staff.

Ventilating extract air units

For protection ventilation, devices for extract air are required that can catch any harmful substances directly at the source or workbench. Lindivent has equipment to control the following laboratory equipment:

  • Fume cupboard
  • Down flow bench
  • Fume hood
  • Local exhaust
  • Safety bench / LAF bench

The equipment is connected to the extract air system. In order for the extract air function to be correct and secured according to regulations, a control unit is required which measures and monitors pressure or airflow to specified setpoints. Continuous regulation is required. Increased flows when, for example, a fume cupboard opens up, momentarily lowers the pressure on the extract air unit. This results in decreased flows elsewhere in the system which must then be corrected.

Flow balance and zone control

Since extract air flows vary and it is critical for the protective function that the correct air direction is maintained even over doors (normally a slight negative pressure is sought in the laboratory to prevent harmful substances from spreading outside the room), the supply air must follow the extract air with an offset, ie a slightly lower flow, with a fast and accurate control function. When a larger fume cupboard closes quickly, an overpressure is created in the room which can cause the spread of dangerous / smelly substances unless the regulation of the supply air follows quickly. In addition to control equipment for specific laboratory equipment, Lindinvent AB has a set of controllers that enable the commissioning of a complete laboratory environment for protective ventilation:

  • Differential pressure control
  • Variable flows
  • Variable and fixed flows
  • Laboratory climate control
NOTE! It´s not only about the equipment:
Operation and working methods are as important to have the desired function.

Systems for controlling, regulating and monitoring protective ventilation aim to:

  • Maintain a safe working environment
  • Minimize leakage from, for example, fume cupboards
  • Compensate for equipment soiling (eg HEPA filter) 
  • Keeping airflow directions through doors and locks intact to minimize the spread of hazardous substances   
  • Alarm in case of deviations in function
  • Minimize energy use
  • Provide staff with operational information and control capability

Formula 1 of ventilation

Protective ventilation corresponds to Formula 1 in terms of accuracy requirements and requirements for reliability and stability. Often, solutions are required that ensure sufficient flow despite a very limited space for the duct system. The following requirements shall be met:

  • High control accuracy
  • Fast regulation
  • Sensitive sensors that can handle large airflow ranges (typically 0.5 m / s - 7.0 m / s)
  • Long service life on damper motors and electronics
  • Long-term stable sensors that are protected against dirt and corrosion
  • Good measurement accuracy despite perhaps short straight distances in the duct system
The energy aspect

A fume cupboard has relatively high flows when open. If staff do not consider closing the door, an automatic door closing may be an option.

In schools you often have chemistry rooms with a fume cupboard where the teacher can show experiments. These rooms then have a need for higher flow when the students are present AND when the fume cupboard is open. Instead of simply changing the flow between the fume cupboard and the general extract air, the flow can be adjusted to the number of people in the room. Such a solution reduces energy consumption, which is often a stated goal.

Design documentation for protective ventilation

Akademiska hus at Karolinska has created a good foundation for designing protective ventilation:
Diskussionsunderlag Skyddsventilation (2001)

Regulations governing safety ventilation etc.
The Swedish Work Environment Authority (Arbetsmiljöverket) specifies requirements for protective ventilation.

Workplace design (Arbetsplatsens utformning AFS 2009:2)

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