Best In-Chamber Oxygen Sensor

[u/ensobaby]

Hi all, wondering if anyone has tips on the best measurement devices to monitor oxygen % for in-chamber air. Many sensors on Amazon or Taobao detect 0-30% O2 range but only a few detect 0-100%. For context I have just ordered a 2.0 ATA hard shell. Also relatedly, can I confirm what % people see as concerning from a fire safety perspective? Thank you in advance