The software is in some hardware. The hardware can be seen and removed, and can be known when it's removed. A chemical can't be seen, and can't be removed. An

The software is in some hardware. The hardware can be seen and removed, and can be known when it's removed. A chemical can't be seen, and can't be removed. And even if the hardware is super entwined with the building, making it hard to remove, such as tied in with the HVAC system, there likely will be some toggle switch to turn off facial recognition. There's no toggle switch to remove chemicals.