fumatorium

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An airtight fumigation chamber in which chemical vapors are used to destroy insects and fungi on plants.

from The Century Dictionary.

• noun A fumatory; specifically, in recent use, an air-tight structure in which small trees or other plants are fumigated to destroy scale or other insects.

from the GNU version of the Collaborative International Dictionary of English.

• noun An air-tight compartment in which vapor may be generated to destroy germs or insects; esp., the apparatus used to destroy San José scale on nursery stock, with hydrocyanic acid vapor.