Wow, that's expensive at US $259-<div>There are a few options on Ali Express that are 0-5000ppm</div><div>for around N.Z. $20- that have good reviews. However I am not an expert and wouldnt know if they are good quality. </div><div>They are compatible with Arduino etc. </div><div>You could buy 3 at that price & compare the readings to indicate when they fail. Have a spare one to just unplug and replace.</div><div>Alan</div><div><br></div><div><br><br><div id="ymail_android_signature"><a id="ymail_android_signature_link" href="https://mail.onelink.me/107872968?pid=nativeplacement&c=Global_Acquisition_YMktg_315_Internal_EmailSignature&af_sub1=Acquisition&af_sub2=Global_YMktg&af_sub3=&af_sub4=100000604&af_sub5=EmailSignature__Static_">Sent from Yahoo Mail on Android</a></div> <br> <blockquote style="margin: 0 0 20px 0;"> <div style="font-family:Roboto, sans-serif; color:#6D00F6;"> <div>On Wed, 25 Oct 2023 at 2:07 am, Jon Wallace via Personal_Submersibles</div><div><personal_submersibles@psubs.org> wrote:</div> </div> <div style="padding: 10px 0 0 20px; margin: 10px 0 0 0; border-left: 1px solid #6D00F6;"> _______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br clear="none"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"> </div> </blockquote></div>