OSHA’s says No; 1910.106(e)(2)(iii) does NOT require the exclusive use of fresh air for ventilation purposes. OSHA states that 1910.106(e)(2)(iii) is a performance requirement and does NOT explicitly require the introduction of fresh air to meet the performance requirements of the OSHA standard. OSHA, under §1910.106(e)(2)(iii), expects employers to provide adequate ventilation to maintain concentrations below 25% of the LEL. In other words, if an employer covered under §1910.106(e)(2)(iii) chooses to recirculate air, then the employer must take measures to provide adequate ventilation to maintain concentrations below 25% of the LEL. Note that the recirculation of air for ventilation purposes can result in the reintroduction of already exhausted flammable and combustible materials back to the ventilated area. This recirculation can result in a buildup of flammable and combustible materials in the area being ventilated to rise to concentrations which are considered dangerous, i.e., greater than the 25% of the LEL.