Performance of Home Smoke Alarms - National Institute of ...

In addition, representative electrical and mechanical heat detectors, and residential sprinklerswere included in the test program to provide reference data on activation times. Also includedwere current residential carbon monoxide (CO) alarms employing two of the three sensor typesfound in commercial products (metal oxide and electrochemical cells). The biometric sensorswere not included because they could not be modified for continuous, analog output. The COalarms evaluated are specifically marketed as not being suitable as fire detectors, but rather arefor detecting high levels of CO from malfunctioning or improper use of combustion appliances.However, they were included because they are increasingly being required in addition to smokealarms and because they may be useful in improving performance and reducing nuisance alarmsin conjunction with smoke alarms.All prior studies had been done with ordinary alarm devices that operate on an alarm thresholdbasis – produce an alarm signal when some pre-determined alarm level is exceeded. This limitsthe ability to evaluate the change in performance from variations above or below the setthreshold, and does not allow determination of performance of multiple sensors or of alarmalgorithms. Thus it was decided to include devices that were modified (by their manufacturers)to produce a continuous, analog output signal from their sensor.While greatly increasing the usefulness of the data such modification by the manufacturer raisesthe issue of whether the performance is representative of an unmodified commercial product. Toaddress this the project employed two approaches:• First, there were numerous unmodified devices of the identical model as the analogdevice that were purchased by NIST from local retail sources. These served as acomparison to the analog devices when characterized in NIST’s fire emulator / detectorevaluator (FE/DE) apparatus [5]. The FE/DE is a single-pass "wind tunnel" designed toreproduce all relevant conditions needed to assess the performance of spot-typeparticulate, thermal and gas sensor detectors or combination detectors.• Second, these unmodified devices were used in every test in the room of fire origin.1.3.2 Test Conditions Representative of Current Fatal Residential FiresTo ensure that the room sizes and arrangements, materials of construction, and ventilationconditions are representative of actual dwellings, all tests were conducted in real dwelling units.First, a manufactured home was procured and delivered to the NIST site for use in both fire testsand nuisance alarm tests. The floor plan selected was a three bedroom, two bath arrangementwith a master suite at one end and the other bedrooms at the other end. This size andarrangement represents not only manufactured homes but also apartments and condominiums ofabout 100 m 2 (or about 1000 ft 2 ).5