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

4.2 Sample MassMass loss from the object of fire origin was recorded using a floor-mounted load cell apparatus.Figure 94 shows the apparatus for one of the flaming ignition tests. As the object of fire origin isconsumed by the fire, the mass decreases. The mass was measured over time, yielding theinstantaneous measure of specimen mass, as well as the total mass consumed by the fire. Themass loss rate is simply the rate ofchange of the measured mass loss.It is determined from the slope ofa straight line fit through sevenadjacent points to minimize noisein the instantaneousmeasurements. Mass loss rate isdirectly correlated with thegeneration of combustion products(toxic species, smoke, etc.), aswell as heat release rate.Standard uncertainty for the massloss measurements is expressed asa percentage of the full-scaleresolution of the load cells. Forthe load cell used for these tests,this is approximately ± 2 g. Whilerandom error in the currentexperiments is expected to becomparable to these values,additional uncertainty due tovariation in the ignition and firegrowth of the fire sources fromthis test series can be expected.Replicate tests were conducted forthis report to better quantifyuncertainty.Figure 94. Example of mass loss measurement showingupholstered chair on load cell prior to one of the flamingignition tests and load cell apparatus mounted beneathmanufactured home82