Kitchen Ventilation

Commercial Kitchens


Removal of water vapor, oil, grease, dirt, condensates, odors and other substances that arise during cooking. Kitchen ventilation ducts are probably among those which are the most difficult to clean (and to maintain clean to avoid fires).

Air-duct Requirements

The air ducts should be aerosol-tight.

The surfaces of the air ducts (the inside but also to a certain degree the outside ones) should be smooth and easy to clean and disinfect. In this respect, stainless steel ducts are more appropriate than galvanized steel ones.

Since the detergents required for the cleaning of the ductwork are often liquids or in the form of foams, the air-ducts, fittings and connections should not only be air but also liquid-tight.

The duct sections should be slightly inclined in order to direct the liquids towards the drain-fittings by gravity.

The gaskets should be resistant to the cleaning agents commonly used for the cleaning of air-ducts.

Access doors should be installed every time the ventilation ducts change directions (bends), as well as in front and behind butterfly valves and dampers.

The access doors, like the air-ducts, should be aerosol-tight and oil-tight.

The METU Solutions

METU-FORM system of round ducts, fittings and connections 
Laser welded smooth straight round ducts (from 71 to 1000 mm Ø)
Laser or MIG-welded fittings (from 71 to 1000 mm Ø)
Smooth surfaces (VDI 18869 Part 4)
Available in galvanized or stainless steel 1.4301 / V2A (ZI-101)
Air-tightness above the highest class D according to the norm DIN EN 12237
Oil and aerosol tightness class ATC 1 according to the norm DIN EN 16798-3
Liquid-tight connections with integrated NBR seal (VDI 2052)

Liquid-tight access doors RD and RRD with NBR gasket.
Access doors with silicon gasket (SI) resitsing temperatres up to 200°C.

Air-duct washing out operations

Drain fittings for rectangular and round ducts (ST-G and ST-K)
Drain fittings the oil-gutters on kitchen hoods (ST-K)

Ductwork cleaning companies can work with liquid detergents without worrying about leaks. The smooth inner surfaces (VDI 18869 Part 4) of the METU-FORM ducts allow an efficient cleaning. Cost and time are saved.

1.   Kitchen hood
2.   Liquid detergents
3.   Laser-welded straight ducts
4.   Laser-welded and MIG-welded fittings
5.   Oil-tight SRX Joining Clips with NBR gasket
6.   Access doors for commercial kitchens
7.   ST-K Drain Fittings

Access Doors for Commercial Kitchens

We recommend to use the liquid-tight access doors (RD with NBR gasket and RRD with NBR gasket), tightness class ATC1 according to the EN 16798-3). The NBR seal is largely resistant to oils and greases. In view of the sometimes complicated conditions in kitchens, minor leaks cannot be completely ruled out. The suggested solution is nevertheless the most suitable one from our product range.

Finally, we could install standard access doors with polyethylene (PE) gasket. The PE gasket is only partially resistant to organic oils and greases (see ZI-201). Also, it will soon be soaked with oil and grease and start leaking.


Air-ducts with a slope


1.   90° Elbow minus about 3°
2.   Spacial 3° degrees ebow
3.   Elbow with a non-standard angle
4.   Slope
5.   Drain fitting ST-K
6.   Oils (process industry), condensation, liquid detergents (Kitchens), etc.



The use of ozone and other photochemical processes (UV-light) can lead to accelerated oxidation of steel (galv. and stainless steels), gaskets and other air-duct components.

A Few Norms and Guidelines

VDI-Guideline 6022
Hygiene Requirements for Ventilation and Air-conditioning Systems

VDI- Guideline 2052
Ventilation Equipment for Kitchens

DIN EN 16282
Equipment for Commercial Kitchens - Ventilation Components in Commercial Kitchens

DIN EN 12237
Strength and leakage of circular sheet metal ducts

DIN EN 16798-3
Performance requirements for Ventilation and Room-conditioning Systems

Guideline M-LüAR
Fire-protection Directive for Ventilation Systems

Special kitchen hoods

The METU-FORM air-ducts are liquid-tight (VDI 2052, DIN EN 16282-5, ATC1 according to EN 16798-3). Cleaning companies can therefore use liquid detergents without worrying about possible leaks. The smooth inner duct surfaces (VDI 18869 Part 4) allow efficient cleaning operations, which translate into substantial cost and time savings.

Duct inclination

It is recommended to install the ducts with a certain gradient (slope) in order to allow liquids (condensation, liquid detergents, foams)) to flow towards the drainage points (see also the drain fittings).

  • Commercial kitchens
  • Gastronomy, hotel industry, canteens
  • Kitchen ventilation and kitchen extraction
  • Kitchen exhaust systems
  • Smooth pipe system
  • Liquid-tight ducts facilitate the cleaning operations
  • Extraction of oil mist and fatty fumes and vapors
  • Planning commercial kitchens
  • Kitchen ventilation technology

Small angle elbows for air ducts with a gradient