Fundamentals and Applied Science
Fundamentals and Applied Science tests the physical, chemical, biological, and mathematical reasoning behind exposure and hazard decisions: fire science, gas behavior, ventilation, noise, heat, radiation, toxicology, and statistics. Expect calculation items and conceptual items that punish unit errors.
Core rules
- Fire: fire tetrahedron (fuel, oxygen, heat, chain reaction). Flash point is the lowest temperature at which a liquid gives off ignitable vapor; autoignition is spontaneous ignition without a source. LEL/UEL bound the flammable range.
- Unit conversion: at 25°C and 1 atm, ppm = mg/m³ × 24.45 / molecular weight. At 0°C use 22.4.
- Noise: decibels are logarithmic; combine levels with 10 log₁₀(Σ10^(Lᵢ/10)), never by simple addition. The OSHA exchange rate is 5 dB.
- Ventilation: dilution airflow depends on contaminant generation rate and target concentration; local exhaust captures at the source and is preferred for toxic materials.
- Toxicology: dose matters; routes are inhalation, dermal, ingestion, injection; LD50/LC50 describe potency, not safe exposure.
Worked example
A sample shows 100 mg/m³ of toluene (molecular weight 92). Convert to ppm: 100 × 24.45 / 92 = 26.6 ppm. Compare with an 8-hour occupational exposure limit of 20 ppm; the result exceeds the limit, so the exposure is unacceptable and controls are needed. Rounding to 27 ppm is fine, but do not compare mg/m³ directly to a ppm limit.
Traps
- Adding decibels arithmetically.
- Using 22.4 at 25°C or ignoring temperature and pressure.
- Treating LEL as a toxicity threshold.
- Confusing flash point with autoignition temperature.