Table 3.

Exposure limits and HF burns that occupy various BSA depending on the acid concentrations that could have a lethal outcome

Exposure limits	3 ppm* - maximum concentration of a chemical substance that an employee may be exposed to over an 8-hour work shift; eyes and throat irritation, if not protected, have been noted.
	20 ppm** - maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms, which could impair an individual’s ability to leave the contaminated area, and take protective action.
	30 ppm***30 ppm*** - immediately dangerous to health or life concentration.
HF burns with a high risk to develop lethal electrolyte imbalances	1% BSA burn with anhydrous HF
	5% BSA burn with >70% concentrated HF
	7% BSA burn with 50–70% concentrated HF
	10% BSA burn with 20–50% concentrated HF
	20% BSA burn with <20% concentrated HF
	Prolonged exposure or long delay for treatment in minor HF burns
	Ingestion of HF at concentrations >5%
	Inhalation of HF at concentrations >5%

allowed by OSHA*; according to AIHA**; established by NIOSH****1%, BSA is an area equal to a hand palm.