sources of irreducible timing uncertainty described in Section 2 will limit the tightness of the timing requirements that can be applied. The degradation of time resolution for low energy particles requires that any time filtering must take this energy dependence into account in order to avoid biasing the measurement. The timing filter for individual cell measurements was defined according to the resolution measurement shown in Fig. \[fig:timeResEnvelopesAndFilter\]. The filter, shown in Fig. \[fig:timeResEnvelopesAndFilter\](b), is made wider than the 95% confidence level by a factor of two, to allow for the additional uncertainty associated with the spread of primary vertex locations, particularly for the endcap calorimeters. The effect of the primary vertex distribution is expected in collision data and included in the CMS simulation but not included in Fig. \[fig:timeResEnvelopesAndFilter\](b), which is intended to replicate the results of test beam data. The larger envelope is also considered a conservative choice for startup when the detector is expected to be less well calibrated, and other sources of irreducible uncertainty will not yet have been identified. For hits with energies below 4, no requirement is applied except that the peak amplitude should be in the triggered data sample.

Using the strategy outlined above, 