This is a ready-to-use worksheet for assessing a temperature excursion. It computes Mean Kinetic Temperature (MKT), screens against the limits that MKT alone does not cover (instantaneous excursion and freeze), and records the draw-down against the product’s cumulative stability budget. Replace every <<FILL: ...>> placeholder. A worked example follows. MKT supports cumulative storage assessment; it does not replace instantaneous-limit or freeze checks, so this worksheet forces all three.
When to use
Use this worksheet whenever a data logger shows an out-of-range event, or as a routine check on receipt for monitored shipments. Quarantine affected product before dispositioning. The disposition decision belongs to Quality Assurance.
MKT concept and formula
MKT is a single temperature that represents the cumulative thermal stress of a fluctuating profile, Arrhenius-weighted so hot periods count disproportionately. For a series of temperatures over equal time intervals it is computed as:
MKT = (Ea / R) / ( -ln( ( sum of exp(-Ea / (R * T_i)) ) / n ) )
where Ea is the activation energy, R is the gas constant (8.314 J/mol/K), T_i are the interval temperatures in kelvin, and n is the number of intervals. A commonly cited default activation energy is about 83.144 kJ/mol when a product-specific value is unavailable; use the product-specific value when you have one and record which you used.
Section A: excursion identification
| Field | Entry |
|---|---|
| Product and batch/lot | <<FILL>> |
| Labeled storage range | <<FILL: e.g. 2 to 8 degrees C>> |
| Logger ID and calibration status | <<FILL>> |
| Trace source (raw file retained?) | <<FILL: Yes/No>> |
| Excursion window (from / to) | <<FILL>> |
Section B: MKT calculation table
Enter the temperature at each equal time interval across the assessment window. Convert to kelvin (K = C + 273.15).
| Interval | Duration | Temp (C) | Temp (K) | exp(-Ea / (R * T)) |
|---|---|---|---|---|
| 1 | <<FILL>> | <<FILL>> | <<FILL>> | <<FILL>> |
| 2 | <<FILL>> | <<FILL>> | <<FILL>> | <<FILL>> |
| … | ||||
| n | <<FILL>> | <<FILL>> | <<FILL>> | <<FILL>> |
| Sum | <<FILL: sum of column>> |
MKT (K) = <<FILL>> MKT (C) = <<FILL>> Activation energy used: <<FILL: kJ/mol and source>>
Section C: three-part screen (all must pass)
| Check | Limit (from stability data) | Observed | Pass/Fail |
|---|---|---|---|
| Instantaneous maximum | <<FILL: e.g. must not exceed 25 degrees C>> | <<FILL: max reached>> | <<FILL>> |
| Instantaneous minimum / freeze | <<FILL: e.g. no exposure below 0 degrees C>> | <<FILL: min reached>> | <<FILL>> |
| Cumulative (MKT or time-out-of-range) vs budget | <<FILL: e.g. MKT within elevated-storage threshold; cumulative time-out-of-range within budget>> | <<FILL>> | <<FILL>> |
A freeze failure for a freeze-sensitive product is an automatic reject regardless of remaining budget, because freeze-induced aggregation is generally irreversible.
Section D: cumulative stability budget draw-down
| Field | Entry |
|---|---|
| Total allowed budget (from stability) | <<FILL: e.g. 120 h between 8 and 25 degrees C over shelf life>> |
| Prior cumulative consumed | <<FILL>> |
| This excursion contributes | <<FILL>> |
| New cumulative total | <<FILL>> |
| Remaining budget | <<FILL>> |
Section E: disposition
| Field | Entry |
|---|---|
| Decision | <<FILL: accept / accept with reduced dating / quarantine for testing / reject>> |
| Basis (rule and data cited) | <<FILL>> |
| Deviation reference (if raised) | <<FILL>> |
| QA disposition (name, signature, date) | <<FILL>> |
Worked example
A 2 to 8 degrees C biologic. Stability data allows up to 120 hours cumulative between 8 and 25 degrees C over shelf life, and zero exposure below 0 degrees C. Receiver downloads the logger and finds a 9.5-hour warm event.
Section C screen:
| Check | Limit | Observed | Pass/Fail |
|---|---|---|---|
| Instantaneous maximum | Must not exceed 25 C | 17.2 C | Pass |
| Freeze | No exposure below 0 C | Min 3.1 C | Pass |
| Cumulative vs budget | Within 120 h budget | See Section D | Pass |
Section D draw-down:
| Field | Entry |
|---|---|
| Total allowed budget | 120 h between 8 and 25 C |
| Prior cumulative consumed | 22 h |
| This excursion contributes | 9.5 h (MKT for window 12.6 C) |
| New cumulative total | 31.5 h |
| Remaining budget | 88.5 h |
Disposition: accept. No freeze, instantaneous maximum well below the limit, cumulative 31.5 of 120 hours. Log 31.5 hours against the budget ledger, restore status, and raise a deviation for the root cause (a 9-hour customs hold). Contrast: had the trace shown 30 minutes at -3 C, the freeze check fails and the product is rejected regardless of the 88.5 hours of budget that remained.
Common inspection findings this worksheet prevents
- MKT computed and passed, but a short freeze that destroys the product was never checked.
- Each excursion assessed in isolation, so cumulative budget silently overruns across many small events.
- Disposition made by gut feel with no stability-justified rule cited.
- Activation energy assumed but never recorded, so the MKT cannot be reproduced.
- Raw logger file discarded, so the trace behind the decision cannot be verified.
How to adapt this worksheet
- Enter your product’s stability-justified instantaneous limits, freeze rule, and cumulative budget from the stability report.
- Use the product-specific activation energy where one exists; otherwise record the default you used.
- Keep a per-product cumulative budget ledger so Section D reflects true lifetime consumption, not one shipment.
- Route any out-of-budget or freeze result to a formal deviation and QA disposition.
- Retain the raw logger file as the original record behind every calculation.