Adjustable blade louvers are used where air flow is varied in velocity and control of flow must be provided. Grille type louvers are normally associated with air conditioning, where air must be diffused in random flow, avoiding higher velocity air flow patterns. Fusible link louvers are used in fire doors where flames and intense heat passage must be controlled. The link release temperature ecommended is 135°F (57°C).
These louvers must be labeled and may not exceed 24" x 24". Fusible link louvers are allowed only at the bottom of fire doors. Since closing is heat activated, these louvers are not to be used on smoke control doors. Pierced louvers, available from some steel door manufacturers, offer a flush condition and may be furnished with internal insect screens. Louvers are formed by embossing the door face sheets. Louver size determinations As a guide, the following approximate percentages of louver
size may be used to determine the free area in a given size louver: Pierced louver 20% Inverted “V” inserted louver 50 – 60% Inverted “Y” (chevron) inserted louver 40 – 60% “Z” type inserted louver 40 – 45% Adjustable inserted louver 40 – 50% Lightproof inserted louver 20% Fusible link inserted louver 45% The above percentages assume there is no air pressure drop from one side of the door to the other. On air condition grilles an air pressure drop is normal. An average 70% of the grille size can be used in computing free area on doors with air condition grilles. The percentages noted above are approximates. Consult the individual manufacturer’s literature for the specific sizes and ratings normal to their program. A combination of glass lites and louvers is common in steel door work. Care should be taken to avoid specifying too long a narrow lite when a louver or grille occurs in the bottom of the same unit. In addition, handicap codes may dictate the location of the louver relative to the bottom of the door.