I. A student lives in an apartment with a floor area of $60m^2$ and ceiling height of $1\mathrm{.}8m.$ The apartment

has a fresh $($outdoor$)$ air exchange rate of $\frac{0\mathrm{.}5}{h}r.$ The stove in the apartment heats by natural gas. The

student cooks a meal using two gas burners that each emit carbon monoxide $($CO$)$ at a rate of $100m\frac{g}{h}r.$

The outdoor $CO$ concentration can be assumed to be negligible $(0ppm).$ The initial $($time $=0$ indoor $CO$

concentration can be assumed to be $0ppm($except for problem $4).$ Carbon monoxide can be considered

as an inert gas, i$.$e$.,$ it does not stick to or react with any surfaces or other gases in air.

Assume that the student cooks for a long enough period of time to achieve a steady$-$state CO

concentration in the apartment. What is that concentration in $ppb?$

Assume that the student cooks for only $45$ minutes and turns off both burners at that time. What is

the $CO$ concentration in $ppb$ at the end of $45$ minutes?

Repeat problem $2$ for air exchange rates that vary from $0\mathrm{.}1$ to $\frac{1}{h}r$ and plot the concentration at $45$

minutes $($in ppb$)$ versus air exchange rate.

Assume that for the conditions of problem $2,$ the student waits $25$ minutes after turning the burners

off and then starts cooking again with two burners on$.$ How long will it take to reach a concentration

that is $95\%$ of steady$-$state under this condition?

Note that you can actually address this question with an eloquent mathematical derivation $($preferred$)$

or simply by crunching the concentration profile in a spreadsheet.

What is the concentration at $95\%$ of steady$-$state?

Compare your result with the time that would be required to reach $95\%$ of steady$-$state had the initial

indoor $CO$ concentration been $0ppm.$