The risk of fire inside the autoclave is real, although it involves a very specific combination of factors.

When a bag loses its vacuum, the rapid airflow through the bag (from -0.9 bar to the autoclave pressure) can generate an electrostatic charge. This charge may produce a spark, which can ignite a fire if solvents are present inside the bags.

While this is a rare and complex combination, it has occurred.

The phenomenon is connected to the following factors:

1. Use of compressed air as the pressurization medium in the autoclave.
2. Presence of prepreg/resin or other plastics with low combustion thresholds, combined with the percentage of oxygen in the compressed air.
3. Potential for sparks caused by electrostatic charges, arising from contact between materials with different electrical potentials.
4. Combustible materials such as paper, sealing tape, labels, tissues, or similar items inside the autoclave.

In these conditions, a spark caused by electrostatic charges can ignite a brief fire. Typically, the fire is short-lived because it lasts only as long as oxygen is present.

Unless there are process anomalies, there is no risk to the structural integrity of the autoclave.

If nitrogen is used instead of compressed air, these fire risks are eliminated, since nitrogen is an inert gas.

Regardless, we strongly advise replace all safety devices and systems responsible for controlling pressure and temperature (atmospheric pressure switch, hi pressure switch, hi temperature thermostat, autoclave's internal pressure transducer)