Answer to Question 1
ARI standard air is defined as air weighing 0.075 lb/ft3 which approximates dry air at 70F and at a barometric pressure of 29.92 in Hg
Answer to Question 2
Soot is formed when the gas is not burning completely. This is caused by too much gas or too little air. Adjust the gas to air ratio by decreasing the gas or increasing the air.