Sampling Methods and Field Procedures for Paint, Dust, Soil, and Water
Paint Sampling
The candidate must know the difference between XRF (field measurement of lead in paint) and laboratory paint chip analysis. XRF readings are reported in mg/cm² and are affected by substrate (e.g., brick, metal) and by the instrument's calibration. Paint chip samples are collected by removing a defined area of paint down to the substrate and submitting it for laboratory analysis by weight percent or mg/cm². Do not burn or melt paint during collection.
Dust Sampling
Dust wipe sampling uses a template to define an area (commonly 1 ft² or 100 cm²) and a wipe to collect dust from sills, floors, and window troughs. The wipe must be placed in a clean container, and the sampled area must be recorded. Wipe sampling is the standard method for dust; vacuum methods exist but are less common for clearance.
Soil Sampling
Soil samples are collected from bare soil areas, typically the top ½ inch, using a clean scoop or core. Sample depth, location, and whether the area is bare or covered must be recorded. Composite soil samples may be used for screening but individual samples are needed for hazard determination.
Water Sampling
Water is sampled after a defined stagnation period, typically using a first-draw sample from a tap that has not been used. The candidate should know that water is not a primary lead source in most housing but can be relevant in older plumbing.
Traps in Questions
Common traps include confusing mg/cm² with percent by weight, using a composite for clearance dust, sampling soil too deep, and forgetting to record the sampled area for wipes. Also watch for XRF substrate interference and the need for calibration checks.
Rule of Thumb
For dust wipes, always record the exact area sampled - the result is a concentration, and without the area the number is meaningless.