Modifying an industrial heater to have an exhaust function

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Hi, I have a Reznor f400 industrial heater that is used to heat a large warehouse space. The unit is gas powered and heats air blown across a large burner by way of a fan that sits in the rear of the unit. The fan in my model runs on a Fasco D701 motor. Just in front of the fan and on the top of the unit is a vent shaft that leads to the roof.

The space can become quite warm in the summer months. There is considerable flow of air into the space through the use of air circulators but venting air has been a problem. I'm considering the possibility of installing an inline fan in the heater vent shaft in addition to reversing the Fasco fan native to the heater. Potentially these modifications could pull hot air from the space? Thoughts?

Thanks