Specifications for UL Smoke Box 1.pdf

Smoke Box Test System Specifications

CPSC is seeking a smoke box for conducting tests on smoke alarms in accordance with UL 217 – Smoke Alarms. The smoke box shall comply with the following construction specifications:

1) Smoke box

a. A DC type microammeter having a maximum internal resistance of 100 ohms and full scale reading of 100 mA used with a barrier type selenium photovoltaic cell, enclosed in a hermetically sealed case, to measure the visible smoke/aerosol obscuration (optical density) in the test compartment

i. An equivalent meter consists of a digital voltmeter having a minimum i nput impedance of 10 megohms in parallel with a 100 ohms resistance, and a 500 ohms potentiometer. The meter and cell shall be used in conjunction with the light produced by a tungsten filament automotive type lamp (such as a prefocused spotlight bulb) energized from a constant current source at half rated voltage to provide a light beam of uniform flux density. The photoelectric cell and lamp shall be spaced 1.524 m (5.0 ft.)

apart.

b. The chamber configurations shall provide a homogeneous smoke/aerosol mix and a laminar air flow across the unit under test (smoke alarm), adjustable from 0.16 to

0.76 m/s [30 to 150 feet per minute (fpm)].

c. Outer Cabinet – Constructed of 19.1-mm (3/4-in.) exterior grade plywood, and having overall inside dimensions of 1.67 m (65-3/4 in.) length by 464 mm (18-1/4 in.)

depth by 460 mm (18-1/8 in.) width. Has a centrally located gasketed hinged top door 860 mm (33-7/8 in.) wide in the top with a 368 by 610-mm (14-1/2 by 24-in.)

clear plastic window. A 6.4-mm (1/4-in.) diameter hole is located in the window center for air flow measurement.

d. Box is provided with a 178-mm (7-in.) diameter exhaust port in the right end, centered 114 mm (4-1/2 in.) above the bottom and employed with a sliding or hinged wooden cover.

e. Inner Compartment – Constructed of 19.1-mm (3/4-in.) plywood, having inside dimensions of 1.06 m (41-3/4 in.) length by 292 mm (11-1/2 in.) height covering the entire width of the inside of the outer cabinet. The left end has a 102-mm (4-in.)

diameter hole for the 30 – 35 fpm circulating fan centered 114 mm (4-1/2 in.) from the side and 98 mm (3-7/8 in.) from the bottom rear corner, a 146-mm (5-3/4-in.)

diameter hole for the 150 fpm circulating fan centered 96.1 mm (3-7/8 in.) above the bottom, and a 102-mm (4-in.) diameter hole for the light beam centered 76.2 mm (3 in.) in either direction from the top back corner. The right end is the same as the left end except that it has one additional 102-mm (4-in.) diameter hole centered 76.2 mm (3 in.) in either direction from the top front corner. Nominal 15.9-mm (5/8-in.)

molding strips are used to secure the end pieces and the top. All interior surfaces are painted with a flat black paint.

f. Circulating Fan 91 mpm (300 fpm)c – sized sufficient to obtain 91 mpm (300 fpm).

The fan, located on either side of the opening, is connected to a motor controller (autotransformer) or equivalent to adjust speed.

g. Photocell– Selenium barrier layer type, 1.5-in (38-mm) diameter for active area.

Photovoltaic cell active material is sealed against environment and mounted on a 19.1-mm (3/4-in) plywood bracket 27 mm (5 in) behind a panel that has a 63.1-mm (2-1/2-in) diameter hole to limit the detection of forward-scattered light. Photocell has a 25 percent maximum deviation from true linearity at 2152 lm/m2 (200 ft-candles) with a 200 ohm load resistance, and has a sensitivity of 0.416 ±0.046 microamperes per lm/m2 (4.4 ±0.3 microamperes per ft-candle) flowing through a 200 ohm load (meter resistance or other). The photocell (in use) is loaded with a nominal 100 ohm,1 percent load, trimmed with a 10,000 ohm, ten turn potentiometer placed across the loaded photocell in a configuration which has negligible effect on the total photocell load regardless of the potentiometer setting and is nominally illuminated at 236.7 lm/m2 (22 ft-candles). Spectral response peak is between 530 and 580 nanometer with 30 percent sensitivity response at 350 and 660 nanometer.

h. Airstream Deflector – Constructed of sheet aluminum, 457 mm (18 in) wide by 394 mm (15-1/2 in) long, secured at each end by screws to two 19.1-mm (3/4-in) thick plywood sections; each section is to be 219 mm (8-5/8 in) high, 235-mm (9-1/4 in) long (adjacent to top of test box) with a 254-mm (10-in) radius curved section to which the deflecting plate is to be attached. The plate is to extend 25.4 mm (1 in) beyond the upper edge and 15.9 mm (5/8 in) beyond the lower edge. Each plywood cutout is to be secured to the side wall of the test compartment.

i. Airstream Straightener – Constructed of aluminum honeycomb, nominal 6.4 mm (1/4 in) cell size; overall dimensions shall be 178 by 457 by 76 mm (7 by 18 by 3 in).

When an equivalent honeycomb is employed the cell size length-to-diameter ratio shall be greater than 10.

j. Screen – Constructed of screening material of 0.3-mm (0.01-in) aluminum wire, having nominal 1.6 mm (1/16 in) square openings, 460.0 mm (18-1/8 in) long by 178 mm (7 in) wide. To be wedged adjacent to airstream straightener.

2) A cotton lamp wick, nominally 3.2 mm (1/8 in) in diameter and minimum 80 meters

3) A computer, software, and data acquisition system to track and record the smoke obscuration measurements within the smoke box

4) DC power supply to power the equipment within the smoke box