Cleaning
Cleaning removes the fuel, residue, and odor source. The exam tests residue identification, cleaning sequence, chemical selection, and surface safety.
Core rules
- Identify residue: wet smoke is sticky, smoldering, low-heat; dry smoke is powdery, high-heat; protein residue is nearly invisible, greasy, and pungent; fuel-oil soot is oily and spreads easily.
- Remove dry residue before wet cleaning: HEPA vacuum, dry sponges, then chemical sponges.
- Use the cleaning equation: time, agitation, concentration, temperature. More chemical is not a substitute for dwell time or mechanical action.
- Work top-down and from clean to dirty; test chemicals on hidden areas; rinse residues; dry promptly.
- Match method to surface: alkaline cleaners for greasy protein and soot; solvents for adhesives; abrasive methods only where the surface tolerates them.
- Prevent cross-contamination: change sponges and cloths; control runoff.
Worked example
A stovetop protein fire leaves little visible char but a strong odor throughout a house. A helper begins wet-wiping walls with a strong solvent. Reasoning: protein residue is greasy and often alkaline-soluble; solvent smears it and spreads odor. The correct approach is HEPA vacuuming, cleaning with an alkaline degreaser at the stated dilution, allowing dwell time, rinsing, and drying. Visible cleanliness alone is not the endpoint; odor source removal is.
Traps that cost marks
Wetting dry smoke before vacuuming; using one cleaner on every surface; skipping rinsing; over-wetting porous materials; cleaning from bottom to top; failing to test delicate finishes.