Monitoring for Radon-222 Emissions – USEPA Method 115
USEPA Method 115 describes the monitoring methods which must be used in determining the radon-222 emissions from underground uranium mines, uranium mill tailings piles, phosphogypsum stacks, and other piles of waste material emitting radon.
 
Radon-222 emissions from underground uranium mine vents is determined using one of the following methods:

• continuous measurement
• periodic measurement

Continuous measurements are made and the emissions calculated by continuously measuring the radon-222 concentration at each mine vent whenever the mine ventilation system is operational.  Each mine vent exhaust flow rate is measured at least 4 times per year.  A weekly radon-222 emission rate for the mine is calculated and recorded weekly.
 
Periodic measurements are continuously performed at each mine vent for at least one week every three months.  Each mine vent exhaust flow rate is measured at least once during each of the radon-222 measurement periods.  A weekly radon-222 emission rate is calculated for each weekly period according to the method.
 
Periodic measurement is applicable only to mines that continuously operate their ventilation system except for extended shutdowns. Mines which start up and shut down their ventilation system frequently must use the continuous measurement method.