Halon is now illegal to use for data center fire suppression. What is the reason it was outlawed?

While Halon can displace oxygen, the primary reason for its ban was environmental, not direct threat to human safety upon deployment, especially compared to its ozone depletion potential.

Halon was banned primarily because it contains ozone-depleting substances, such as bromine and chlorine, which cause severe damage to the Earth's stratospheric ozone layer, contributing to global environmental degradation.

Halon was highly effective at suppressing fires, which is why it was widely used before its environmental impact became fully understood.

Halon is a 'clean agent' and was specifically valued for not causing undue damage to electronic systems, unlike water or other extinguishing agents.