The us ambient air-quality standard for co is 40 mgm3 how

Question

An ice rink, depicted in figure 4-22, has the following condition:

at the time the resurfacing machine is turned off.

(a) What is the mass flux of CO out of the control volume at this moment, in units of mg/s?

(b) The U.S. ambient air-quality standard for CO is 40 mg/m³. How long would it take before the CO concentration in the well-mixed ice rink air dropped to 40 mg/m³? Express your answer in units of hours.