Where the fan is to run on alternating current, the 9, 12, or 16 inch size may be installed, with capacity ranging from approximately five hundred to 1575 cubic feet of air per minute. The nine-inch blade is finished in dull brass, the larger models in black enamel. If the current is direct, only the sixteen-inch fan is available. A feature of the larger fans is the speed regulating switch.

The twelve-inch fan of D sets in a metal window panel, with inserts of a translucent substance to let the light through. The smaller panel will extend to fit a window up to 34 inches wide; the wider panel accommodates a window up to fifty-inch width. This silent fan, made by a company of long established reputation, handles 625 cubic feet of air per minute with its special blade. And it may be used either as an exhaust fan or as an air intake.

E is an exhaust fan only, and may be had in set-in glass or steel panels for the double-hung window, in the transom model or in the wall-cabinet type. It may also be had without panels of any kind. The extension window panels, with their chrome plated frame and aluminum parts, fit windows of widths from 17" to 63", and are as easily put up as a window shade. The transom model, finished in pearl-gray enamel, is adjustable to fit transoms from 26" to 36" wide. The ten-inch blades of the patented propeller will pull out 800 cubic feet of air per minute. The motor is non-radio interfering, and operates with little noise.

F is a handy portable window ventilator, easily installed, being composed of two sturdy brackets which fasten to the window casing, and the frame in which the fan is mounted. It will quietly exhaust 900 cubic feet of air per minute.

G. This ventilator may be inserted in the window, its gray, white or lacquered metal panels being adjustable in three sizes, to windows ranging from 25" to 42". Or the cabinet type, with its one-handle control, may be built right into the wall of the new home. The manufacturers of this quiet and efficient device feature a special, insulated, slow-speed motor which will operate continuously twenty-four hours a day, if desired, without becoming hot. The fan delivers a maximum of 600 cubic feet per minute, without objectionable noise, and a variable speed regulator can be added.

H. Polished aluminum is the material of which this simple window ventilator is made. The fan has a thirteen-inch blade and is mounted on an adjustable mounting board, to fit any width of window. Neat, compact, light and rustless, it has a reversible motor to draw out or blow in the air, and can be supplied for any current.

I. Again the window, transom and cabinet models are offered in this fine ventilator. The window type is set in steel or glass with aluminum mountings, adjustable to fit windows from 17" to 50" wide. The transom and cabinet types are finished in soft gray enamel, the former adjustable to transoms 26" to 36" wide. The manufacturers claim that their ten-inch propeller will deliver 40 per cent more air than other makes - 800 cubic feet per minute being its capacity. The considerable variation in prices depends on the type and kind of current used.

J. Another good type, this - economically installed in the window on its portable wood panel, or built permanently into the wall in the cabinet type. The patented fan alone may also be purchased. The white mounting panels for the window type come in three widths - 36", 42" and 48"- while the green ventilator is either a twelve-inch fan or a sixteen-inch size. The twelve-inch can handle 750 cubic feet of air per minute; the sixteen-inch 1000 cubic feet. The manufacturers of this ventilator claim that it is the only motor-driven exhaust fan with a fully enclosed, self-cooled motor.