Chemoreceptors in the circulatory system detect changes in circulating pco2. if co2 concentrations get too high, the rate of ventilation increases. why does this make sense?

The more active cells produce more carbon dioxide.

Explanation:

When the cells are constantly working the amount of oxygen consumed and more amount of carbon dioxide is released by the cells.

Chemo receptors in the circulatory system increases the ventilation so that more carbon dioxide can go out of the cell and more oxygen can get inside the cell.

This is because the more active cells more carbon dioxide and there is a sudden increase in the concentration of carbon dioxide which need to be corrected by the help of ventilation.