Slide 4-2 Radon units Picocuries/liter ( pCi/L) Measures Activity (decays/minute) per volume (one liter of air) 1 pCi/L = 2.22 decays per minute per liter of air What is the EPA action level in terms of decays per minute per liter of air?
Slide 4-3 EPA action level Picocuries/liter 4 pCi/L = 4 x 2.22 decays/minute/liter = 8.88 decays/minute/liter Question Assume that a client spent 10 hours/day in a room with a radon level of 4 pCi/L. How many decays/liter would the client be exposed to each day? Answer 5,328 decays/day/liter
Slide 4-4 International System (SI) Radioactivity units 1 becquerel (Bq) = 1 decay/second = 27 pCi 1 pCi = decays/second = Bq Henri Becquerel, discovered radioactivity in 1896
Slide 4-5 International System (SI) Radon units 1 pCi/L = 37 Bq/m 3
Slide 4-6 EPA action level International System (SI) 4 pCi/L = 4 x 37 Bq/m 3 = 148 Bq/m 3
Slide 4-8 Measuring RDPs Working level (WL) 1 WL = Concentration of RDPs produced from one liter of air that contains 100 pCi/L of radon = Amount of short-lived RDPs that exists at a single moment if a container is kept at a constant 100 pCi/L
Slide 4-13 Factors that affect radon and RDP concentrations Some radon gas and RDPs escape as air flows out of home Some RDPs attach to (plate out on) solid objects, such as –Walls –Floors –Ceilings –Furniture Plating out Lowers RDP concentration in air Plated out RDPs cannot be measured Only RDPs in air can be measured Factors that affect plating out also affect measurement of RDPs
Slide 4-14 Factors that affect radon and RDP concentrations Air circulation –Air moving within a room Ventilation –Fresh air entering a room Air filters Particles suspended in the air –Dust –Smoke –Aerosols Some RDPs plated out
Slide 4-15 Air circulation Circulation = moving around air already in a room How would air circulation affect concentration of RDPs? May increase plating out, as RDP particles blow toward solid objects and attach to them As plating out increases, concentration of RDPs in the air decreases Fans increase normal air circulation
Slide 4-16 Ventilation Ventilation = supply of fresh air How would ventilation affect concentration of RFDs? Ventilation likely to lower concentration of RFDs May also reduce radon concentration, as gas escapes from home Open windows and doors increase ventilation
Slide 4-17 Air filter How would air filters affect concentration of RFDs? Air filters may remove some RDPs, which –Are particles –Have electrical charge –React chemically Example Furnace air filter Air filters will not remove radon, which –Is a gas –Has no electrical charge –Does not readily react chemically
Slide 4-18 Particles suspended in air Examples –Dust –Smoke –Aerosols How would particles affect concentration of RDPs? RDPs are more likely to attach to particles RDP concentration in air decreases
Slide 4-19 Factors may affect radon measurement Air circulation Ventilation Air filters Particles in the air
Slide 4-20 Secular (eventual) equilibrium Radon Radon decay products Radon In closed home, concentration of RDPs increases until secular equilibrium is reached –Means RDPs have same level of radioactivity as radon itself –Takes 3-4 hours –Measure home after it has reached secular equilibrium At secular equilibrium, 1 WL = 100 pCi/L
Slide 4-21 A home inspector’s lament and pledge Picocuries and becquerels; secular equilibrium. Radon decaying has made my brain cells go numb. But I do understand: breathing radon’s not healthy, So I’ll master these concepts, though they won’t make me wealthy. Convert all these measurements? Curse that uranium! I’m working at levels that hurt my poor cranium. I’ll learn proper techniques, use the right protocol, To help prevent cancer: that’s the goal of my role.