Which sterilization phase usually takes the longest?

For ethylene oxide, aeration often does, because residual gas must leave the load before release. For steam, conditioning and exposure dominate. The verdict names the longest phase at your own inputs.

Why does the allowance apply to process hours?

Handling and documentation scale with the work a cycle generates, so the allowance is charged as a share of the summed phase hours. If you have timed the load moves, enter those hours directly and set the allowance to zero.

Can two phases of one cycle overlap?

Not in one chamber: conditioning, exposure, evacuation and aeration run in sequence on the same load. Overlap only comes from staggering several chambers, which this page does not model.

Why does aeration count when the device is already sterile?

Aeration is not sterilization: it removes residual ethylene oxide until residue limits are met. It still occupies the sterilizer and delays release, so it belongs in cycle time.

MedTech Manufacturing calculator

Sterilization Cycle Time Calculator

Add up the four phases a sterilization cycle runs, then the handling and documentation around them. The page reports the phase total, the allowance hours and the longest phase.

What this calculator does

Hours one sterilization cycle ties up a sterilizer and load, from its four phases plus a handling and documentation allowance.

Formula used

Process hours = conditioning hours + exposure hours + evacuation hours + aeration hours
Handling hours = process hours × handling and documentation allowance ÷ 100
Total cycle time = process hours + handling hours
Longest phase = the largest of the four phase hour inputs

Inputs explained

Conditioning Hours: Hours to precondition the load: vacuum, humidity and temperature.
Exposure Hours: Hours at the sterilant setpoint, gas dwell or steam plateau.
Evacuation Hours: Hours to strip sterilant with vacuum pulses and washes.
Aeration Hours: Hours to aerate the load until residue limits are met.
Handling and Documentation Allowance: Load handling, indicator placement and records as a share of phases.

How to use the result

Best suited to scheduling sterilizer slots for a launch build, comparing ethylene oxide and steam cycle length, sizing a load's aeration hold before release.
Does not include cooling, post cycle hold, or release testing after aeration. Overlapping cycles on a multi chamber sterilizer need each run entered separately.

Current U.S. benchmarks

U.S. manufacturing runs at 75.7% of capacity with new factory orders at $663B per month (Federal Reserve and Census, Aug 2026).
The U.S. has 8,825 medical equipment and supplies establishments employing about 308,388 workers (Census County Business Patterns, 2023).

Common questions

Which sterilization phase usually takes the longest? For ethylene oxide, aeration often does, because residual gas must leave the load before release. For steam, conditioning and exposure dominate. The verdict names the longest phase at your own inputs.
Why does the allowance apply to process hours? Handling and documentation scale with the work a cycle generates, so the allowance is charged as a share of the summed phase hours. If you have timed the load moves, enter those hours directly and set the allowance to zero.
Can two phases of one cycle overlap? Not in one chamber: conditioning, exposure, evacuation and aeration run in sequence on the same load. Overlap only comes from staggering several chambers, which this page does not model.
Why does aeration count when the device is already sterile? Aeration is not sterilization: it removes residual ethylene oxide until residue limits are met. It still occupies the sterilizer and delays release, so it belongs in cycle time.

Last reviewed 2026-10-01.