Page 175 - Lean six sigma demystified

154 Lean Six Sigma DemystifieD

n = 11 Causes of false fire alarms
11 100%
91%
90%
9.625 82%
80%
8.25 7 64% 70%
Number of false fire alarms 6.875 60%

50%
5.5
40%
4.125

2.75 30%
2
20%
1.375 1 1
10%
0 0%
Faulty detector Cell phone demonstration Water leak Printer dust
Cause
FIGURE 5-2 • Pareto chart of causes of false fire alarms.

Could cell phones cause false fire alarms? We checked with the engineers, and
they said yes, if the detectors weren’t properly shielded from the radio fre-
quency interference (RFI) generated by cell phones. Now all detectors are sup-
posed to be shielded to meet the Underwriters Laboratory (UL) code, so we
guessed that some of our detectors might be unshielded and that unshielded
detectors were the root cause of the false fire alarms (Fig. 5-3).
We had technicians verify that the different kinds of detectors in our building—

photoelectric and particulate—were below UL code and had in fact caused the
false fire alarms. (You have to verify that you’ve identified the root cause. You
can’t just proclaim victory; you have to prove it.)
There were 1,100 detectors in the building and we estimated it would cost
$100 to $200 to replace each one ($110,000 to $220,000). The building was
rented, and we were planning to move out the following year, so we informed the
owner of the problem and devised a simple sign to discourage people from using
cell phones inside the building. These were our countermeasures (Fig. 5-4). Since
we knew that there were 600 people in the building at any time and that the
loaded cost of interrupting their work to exit the building was $50 per alarm,
we estimated that we saved $300,000 in lost productivity by eliminating
10 false fire alarms a year. (Six Sigma is about measuring money saved.)