No. §1910.106(e)(2)(iii) does not require the exclusive use of fresh air for ventilation purposes. Additionally, 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 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.