CPFM Smoke Management & Air Quality 1 — Questions and Answers
Question 1: What meteorological condition is most favorable for smoke dispersal during a prescribed burn?
- Temperature inversion near the surface
- High mixing height with strong transport winds aloft (Correct answer)
- Calm winds with high relative humidity
- Stable atmospheric stratification
Correct answer: High mixing height with strong transport winds aloft
A high mixing height combined with good transport winds allows smoke to disperse both vertically and horizontally, reducing ground-level concentrations.
Question 2: What is a temperature inversion in the context of prescribed fire smoke management?
- When surface temperatures exceed normal seasonal averages
- A layer of warm air above cooler air that traps smoke near the ground (Correct answer)
- A rapid increase in wind speed with altitude
- A sudden drop in atmospheric pressure ahead of a cold front
Correct answer: A layer of warm air above cooler air that traps smoke near the ground
A temperature inversion traps smoke near the ground because the overlying warm air layer prevents upward mixing, creating hazardous air quality conditions.
Question 3: Which pollutant from prescribed fire smoke is the primary concern for human health?
- Carbon dioxide (CO2)
- Nitrogen oxides (NOx)
- Fine particulate matter (PM2.5) (Correct answer)
- Sulfur dioxide (SO2)
Correct answer: Fine particulate matter (PM2.5)
PM2.5 particles are small enough to penetrate deep into the lungs and are the primary health concern from wildfire and prescribed fire smoke.
Question 4: What does 'mixing height' refer to in smoke management?
- The maximum flame height a fire can produce
- The altitude to which convective mixing extends in the atmosphere (Correct answer)
- The height of the visible smoke column above the fire
- The minimum cloud ceiling required for safe aerial ignition
Correct answer: The altitude to which convective mixing extends in the atmosphere
Mixing height is the altitude to which the atmosphere is well-mixed due to convective activity, determining how high smoke can rise and disperse.
Question 5: Which prescribed burn technique typically produces the most smoke per acre due to slower, more smoldering combustion?
- Headfire (burning with the wind)
- Backfire (burning against the wind) (Correct answer)
- Flank fire (burning perpendicular to wind)
- Aerial ignition with helitorch
Correct answer: Backfire (burning against the wind)
Backfires burn more slowly and involve more smoldering combustion, generating more smoke per unit of fuel consumed compared to fast-moving headfires.
Question 6: What is the Ventilation Index (VI) used to estimate in smoke management?
- Oxygen levels at the fire perimeter during active burning
- The atmosphere's capacity to dilute and transport smoke away from a burn (Correct answer)
- Relative humidity of the smoke column at canopy height
- The rate at which smoke particles deposit on the ground
Correct answer: The atmosphere's capacity to dilute and transport smoke away from a burn
The Ventilation Index combines mixing height and transport wind speed to estimate the atmosphere's capacity to disperse smoke away from a burn area.
Question 7: What time of day is generally LEAST suitable for igniting a prescribed burn due to smoke management concerns?
- Mid-afternoon when surface temperatures peak
- Early morning before the atmospheric mixing layer has developed (Correct answer)
- Late morning after dew has burned off the fuels
- Early afternoon when surface winds are typically strongest
Correct answer: Early morning before the atmospheric mixing layer has developed
Early morning burning is problematic because nocturnal temperature inversions are strongest at that time, trapping smoke near the ground before the mixing layer develops.
CPFM Smoke Management & Air Quality 1
What meteorological condition is most favorable for smoke dispersal during a prescribed burn?