Egress. All parts of every multiple dwelling, above the first story, shall have access to 2 independent means of egress either of which is accessible without passing through the other. In the case of multiple dwellings erected after the passage of this act the construction and arrangement of these means of egress shall conform to provisions of section 39. In the case of multiple dwellings erected prior to the passage of this act, wherein all parts are not supplied with the means of egress specified herein, deficiencies in exit facilities may be corrected by the erection of fire escapes constructed and arranged in accordance with the provisions of section 40. Access to existing fire escapes shall be equivalent to the standards established in section 40 for fire escapes. Where there are not more than 2 apartments or 6 sleeping rooms on a floor, access to 1 means of egress may be had through a private room or apartment providing the door to such room or apartment, through which such access is to be had, is equipped with a glass panel and other appurtenances as specified in section 40 for similar access doors to fire escapes.