Yes, it's a good idea to place the drop checker at the point at where CO2 is least 'expected'. This way, if there's 30ppm CO2 there, then there will likely be a minimum of 30ppm CO2 elsewhere.
As a side note - always adjust CO2 slowly and keep an eye on livestock. Some species are more sensitive than others.
As a side note - always adjust CO2 slowly and keep an eye on livestock. Some species are more sensitive than others.