The core point.
A space can look clean and still carry lead-bearing dust at concentrations dangerous to a child. Vacuumed, swept, and visually-inspected floors regularly fail dust-wipe clearance tests. Visible cleanup is not the proof.
Dust-wipe clearance — collecting standardized wipe samples from defined surfaces and laboratory-analyzing them for lead — is the only objective measure that a renovation or abatement has actually returned the space to a lead-safe condition.
Where the thresholds sit.
EPA updated the dust-lead reportable level in 2024, with the new numbers effective January 2025:
- Floors: 5 µg/ft²
- Window sills: 40 µg/ft²
- Window troughs: 100 µg/ft²
These are dramatically tighter than the previous numbers (10, 100, 400) which had themselves replaced an older set (40, 250, 800). The trajectory has been consistent for over a decade: tighter thresholds, smaller permissible residual dust.
Why clearance fails.
The three failure modes we see most often:
- Inadequate HEPA vacuuming. A standard shop vac does not capture fine lead dust. HEPA-filtered vacuums are required, and even then the surface needs multiple passes.
- Wet wiping with the same cloth. A single wet wipe used across multiple surfaces redistributes lead dust rather than removing it. Standard practice is to use a fresh wipe for each surface.
- Trough and sill neglect. Window troughs accumulate the highest dust concentrations and are the most commonly missed. Most failed clearances we re-run are trough failures.
What a clearance sample is.
A pre-moistened wipe meeting ASTM E1792 standards, used in a defined motion to swab a measured surface area, collected under chain-of-custody, and sent to an AIHA-LAP accredited lab for analysis by atomic absorption or ICP-MS. The lab reports micrograms of lead per square foot; the inspector compares to the threshold.
Independence matters.
Clearance is meaningful when the inspector is independent of the contractor who performed the work. EPA and HUD both reference this; NYC HPD expects it for lead violation closure. A contractor self-certifying clearance carries little weight on a regulator's desk.
If you fail clearance.
Re-clean and re-test. There's no shortcut. On Envirex projects, a failed clearance triggers re-cleaning at no charge to the client; we re-sample at the same locations until results pass.