 When Kaga was being designed the problem of how to deal with exhaust gases in carrier operations had not been resolved. The swiveling funnels of Hōshō had not proved successful and wind-tunnel testing had not provided an answer. As a result, Akagi and Kaga were given different exhaust systems to evaluate in real-world conditions. Kaga's funnel gases were collected in a pair of long horizontal ducts which discharged at the rear of each side of the flight deck, in spite of predictions by a number of prominent naval architects that they would not keep the hot gases away from the flight deck. The predictions proved to be correct, not least because Kaga was slower than the Akagi which allowed the gases to rise and interfere with landing operations. Another drawback was that the heat of the gases made the crew's quarters located on the side of the ship by the funnels almost uninhabitable.
