Lesson 4 What are the units for measuring

Lesson 4 What are the units for measuring radon?

Radioactivity units Picocuries (p. Ci) Measures • Activity (radioactive decays/second) • 1 picocurie (p. Ci) = 0. 037 decays/second = 1 decay/27 seconds = 2. 22 decays/minute 1

Radon units Picocuries/liter (p. Ci/L) Measures • Activity (decays/minute) per volume (one liter of air) • 1 p. Ci/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? 2

EPA action level Picocuries/liter 4 p. Ci/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 p. Ci/L. How many decays/liter would the client be exposed to each day? Answer 5, 328 decays/day/liter 3

International System (SI) Radioactivity units 1 becquerel (Bq) = 1 decay/second = 27 p. Ci 1 p. Ci = 0. 037 decays/second = 0. 037 Bq Henri Becquerel, discovered radioactivity in 1896 4

International System (SI) Radon units 1 p. Ci/L = 37 Bq/m 3 5

EPA action level International System (SI) 4 p. Ci/L = 4 x 37 Bq/m 3 = 148 Bq/m 3 6

Measuring radon decay products (RDPs) Measure alpha radiation emitted by shortlived RDPs Polonium-218 Lead-214 Bismuth-214 Polonium-214 7

Measuring RDPs Working level (WL) 1 WL = Concentration of RDPs produced from one liter of air that contains 100 p. Ci/L of radon = Amount of short-lived RDPs that exists at a single moment if a container is kept at a constant 100 p. Ci/L 8

Working level EPA action level 4 p. Ci/L = 0. 02 WL 9

EPA action level Summary • 4 p. Ci/L • 148 Bq/m 3 • 0. 02 WL 10

Questions? 11

Characteristics of radon decay products (RDPs) • Solid particles • Electrically charged • React chemically 12

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 13

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 14

Air circulation • Circulation = moving around air already in a room • How would air circulation affect concentration of RDPs? Fans increase normal air circulation • 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 15

Ventilation • Ventilation = supply of fresh air • How would ventilation affect concentration of RFDs? Open windows and doors increase ventilation • Ventilation likely to lower concentration of RFDs • May also reduce radon concentration, as gas escapes from home 16

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 17

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 18

Factors may affect radon measurement • Air circulation • Ventilation • Air filters • Particles in the air 19

Secular (eventual) equilibrium • 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 p. Ci/L Radon decay products Radon 20

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. 21

Summary EPA action level 4 p. Ci/L = 148 Bq/m 3 = 0. 02 WL 4 4 p. Ci/L = 148 Bq/m 3 = 0. 02 WL See handout 4 -1 22

Summary Factors affecting measurement • Air circulation • Ventilation • Air filters • Particles in the air Importance Factors affect conditions for testing a home 23

Questions? 24

Check your comprehension • See handout 4 -2 25

Check your understanding • See handout 4 - 26