Emission rates from building materials

Certain building materials emit formaldehyde $(HCHO),$ a toxic air pollutant. The following technique is proposed to determine the emissions rate.

Place a sample of material that is to be tested in a CMFR$.$ Close the chamber. The chamber volume is $V{m}^3.$

Supply uncontaminated air into the chamber at a flow rate of $Q\frac{m^3}{s}.$ Allow air to flow out of the chamber at the same rate.

Monitor the HCHO concentration in the outlet air until a steady state concentration is reached $C_{ss}(\frac{g}{m^3})$

Given $V,Q,$ and $C_{ss}$ from such an experiment, what is the HCHO emission rate from the sample in $\frac{g}{s}?$ Assume HCHO is non$-$reactive $($i$.$e$.,$ does not undergo transformation within the CMFR$).$