How far apart should the oxygen and acetylene cylinders be stored?

 Both OSHA and NFPA recommends that oxygen and acetylene cylinders be stored at a minimum distance of 20 feet (6 m) or be separated by a noncombustible barrier of at least 5 feet high.
OSHA 1910.253(b)(4)(iii) – Oxygen cylinders in storage shall be separated from fuel-gas cylinders or combustible materials (especially oil or grease) a minimum distance of 20 feet (6.1m) or by a noncombustible barrier at least 5 feet (1.5m) high having a fire-resistance rating of at least 1/2 hour.
NFPA 51 2-4.3 – Oxygen cylinders in storage shall be separated from fuel-gas cylinders or combustible materials (especially oil or grease) by a minimum distance of 20 ft. (6 m) or by a barrier of noncombustible material at least 5 ft. (1.5 m) high having a fire resistance rating of at least 1/2 hour. The barrier shall interrupt all lines of sight between oxygen and fuel-gas cylinders within 20 ft. of each other.