This paper discusses an extended usage of conventional pressure balances for measurements of pressure down to a few Pa. Generally pressure balances are widely used as pressure standards but they have a major disadvantage, that is, their inability to operate at pressures below a limit determined by the mass of floating elements. This limit is typically around 5 kPa. Several approaches have been tried to reduce this minimum operating pressure, including a tilting piston method, a low-mass piston method, and a variable bell-jar pressure method and so on. Using a variable bell-jar pressure method, we investigated the lowest usable pressure limit. The experiments show that around 5 Pa is the low pressure limit within the required uncertainty.