Laboratory ventilation
In the case of ventilation technology in laboratories , there are increased requirements due to the risk of the transmission of polluted air, which go beyond the regulations for ventilation technology in normal workplaces.
Planning criteria
When planning ventilation in a laboratory, in addition to the provisions for ventilation of workplaces, some additional aspects must be taken into account. When planning every laboratory, it is first necessary to determine which measures must be taken as part of a risk assessment. There may be deviations depending on the intended type of use or the user's level of knowledge. Under various conditions, such as only hourly use, mechanical ventilation is not absolutely necessary. The basic requirements for ventilation and air conditioning systems are:
- the protection of the air we breathe in the laboratory from the penetration of hazardous substances
- taking into account the supply and exhaust air requirements of laboratory equipment
- ensuring adequate indoor air quality
Air exchange rate
An air exchange rate of 25 m³ / h per m² of usable area should be provided for room ventilation in a laboratory. With a room height of three meters, this corresponds to an approximately eightfold air change.
Room accounting
Because the air in a laboratory can be contaminated with pollutants, it is imperative to prevent it from flowing into other rooms. For this purpose, there must be a negative pressure in the laboratory. This can be generated with the help of the ventilation system: A larger air volume flow is extracted from the room than is supplied to it. The difference between the supply and exhaust air is compensated for by the overflow from other rooms; here, in turn, more air is supplied than discharged.
However, depending on the type of laboratory, there may be deviations from these requirements. One example of this is ventilation technology in clean room laboratories : Here it is important to keep the room air free of any contamination. In this case, there must be overpressure in the clean room to prevent air from flowing in from the adjacent rooms.
Because the exhaust air from a laboratory can be contaminated with pollutants, it must not be returned to the building as recirculated air. As a result, the supply air must consist entirely of treated outside air. Notwithstanding this, the room air may be returned to the room in exceptional cases if a hazard from pollutants can be excluded.
Acoustic requirements
A sound pressure level of 52 dB (A) is permissible in a laboratory . In special cases, such as rooms that do not serve as permanent workplaces, higher values can also be set. For planning, however, it is advisable to set a lower value, because a high level of noise at work can be perceived as annoying. When using sound absorbers in the exhaust air, however, greater attention must be paid to possible deposits.
Use of materials
When choosing the material for the ventilation ducts in a laboratory, several criteria must be considered. These include a high level of tightness and good temperature and corrosion resistance of the channels. In addition, they must not contribute to the spread of fire. The following duct materials that meet these requirements can be used for laboratory ventilation:
- Galvanized sheet steel
- stainless steel
- Plastic (e.g. PVC-U)
Exhaust air consumer
Point suction
Point suction systems are provided, for example, for various devices in the laboratory that require air extraction due to contaminated vapors. The point suction is connected to a flexible pipe so that it can be aimed precisely at the equipment. In this way, pollutants cannot be distributed in the room during tests that are not carried out under a fume cupboard.
Safety cabinets
Fire-resistant storage cabinets must have air intake and exhaust openings and be connected to an exhaust air system or to an air intake and exhaust system in the upper and lower part of the cabinet so that the entire volume of the cabinet is ventilated. A constant air change of at least ten must be guaranteed, with a negative pressure in the cabinet. The pressure drop at this point must not exceed 150 Pa.
If toxic gases are stored, a 120-fold air exchange must be ensured. When storing pressurized gas cylinders, the air inlet and outlet openings must close automatically in the event of a fire. If it is a safety cabinet with flammable liquids, this reaction must take place at a temperature of 70 ° C (± 10 ° C).
Rear ventilation of the cabinets
For cabinets that contain, for example, toxic chemicals that do not need to be stored in a safety cabinet, ventilation is necessary. By connecting an exhaust air line, a negative pressure can be created in the cabinets through which no gases can escape from the cabinet. The exhaust air must be permanently discharged so that no hazardous substances can escape outside of operating hours.
Prints
In addition to the requirements for general service fume cupboards, other requirements must also be taken into account for fume cupboards in laboratories. The air flow in the fume cupboards must be designed so that certain threshold values for the concentration of chemicals are not exceeded. In addition, a fume cupboard function indicator must be installed, which can be used to monitor correct functioning. If this is not the case, it must be able to use acoustic and visual signals to draw attention to an error.
Stricter regulations apply to fume cupboards. In the case of high thermal loads, their effect on the air flow must be taken into account. When choosing the sensors, care must be taken to ensure adequate temperature resistance. A temperature sensor must be provided in the fume cupboard so that an alarm can be triggered if the temperature is too high. If a fume cupboard requires the installation of an acid exhaust air washer or an acid sprinkler system, its influence on the air flow must be taken into account.
Air duct system
The regulation of the air flows is of central importance for the air flow in a laboratory. Numerous manufacturers offer various systems for this purpose, which regulate the air supply and removal as required. The control can take place centrally by connecting to the building management system. In addition to this type of control, local operation is also possible.
The air volume flows must be variably adjustable for different operating situations. While fresh air is constantly being supplied to the room, the number and thus also the amount of air extracted by the fume cupboards used varies. When using several extraction devices, the exhaust air that is discharged from the room must be reduced. Alternatively or additionally, the supply air in the room can be increased with the aim of always keeping the balance of supply and exhaust air at the same value. In this way of regulating the air volume, a negative pressure in the room can be permanently guaranteed.
Individual evidence
- ↑ a b c d DIN EN 1946-7, 2009. Air conditioning: Air conditioning systems in laboratories. Berlin: Beuth
- ↑ a b TRGS 526, 2008. Laboratories. Dortmund: BAuA
- ↑ DIN EN 14470-1, 2004. Fire-resistant storage cabinets: Safety cabinets for flammable liquids. Berlin: Beuth
- ↑ DIN EN 14470-2, 2006. Fire-resistant storage cabinets: Safety cabinets for pressurized gas cylinders. Berlin: Beuth
- ↑ DIN EN 14175-2, 2003. Deductions: Requirements for safety and performance
- ↑ DIN EN 14175-7, 2012. Fume cupboards: Fume cupboards for high thermal and acid loads (fume cupboards). Berlin: Beuth