Plan No. 495. Removing Foul Air From Wells
To determine whether or not the air at the bottom of the well is foul, place a lighted torch or lamp in a bucket and lower it into the well. If it continues to burn when the bucket rests on the water, it is safe to descend. If it is extinguished, the air is foul. To remove this, lower a pail filled with burning straw, or by dropping two or three quarts of freshly slaked lime down the well. But test with the light again before descending.
Plenty of people who have wells would gladly pay a small sum to have this information mailed to them.