let's calculate.

article 3.3.4 of code for design of catering buildings, the indoor clear height of kitchen and catering workshop should not be less than 3m.

considering that the distance between columns in public buildings is 8.4 meters, the beam is 611 mm high, which can't be smaller.

suppose there is a dining room above the kitchen, and its floor is made of floor tiles, with a surface layer thickness of 51 mm (111 mm for those with cushions).

the air duct is 311 high.

the smoke exhaust pipe is temporarily considered as 311 meters high, assuming that the smoke exhaust pipe does not cross the air duct and does not occupy the space under the beam.

the spray pipe passing through the beam does not occupy the space under the beam.

the ceiling, keel and ceiling board add up to 51 mm.

the above items add up: 3111+611+51+311+1+51 =4111 (mm) = 4 (m)

This has not considered the gaps between the beam and the air duct, the air duct and the ceiling, and the local elevation of the kitchen floor due to slope finding. Therefore, it is not "too high" to consider the height of the kitchen as 3.9 meters.