Microsoft outage disrupts email-based pool chlorine monitoring, leaving hotel guests injured

Several people were injured after excessive chlorine was pumped into the pool at a hotel in Germany, according to the local TV channel WDR. The report attributes the incident to a malfunction in the dosing system. Chlorine dosing is monitored via email.

WDR reports that the sauna area's "maintenance safety system" attempted to send an email warning that chlorine levels were too high. The email never arrived because Microsoft was experiencing major problems with its Exchange cloud infrastructure at the time. The outage affected numerous services, from hotels and airlines to rail operations.

The incident occurred on Friday afternoon, according to a Facebook post by the responding fire department. A total of 40 first responders were dispatched, as the undelivered email had serious consequences. The fire department said 15 people required triage following a chlorine gas leak. According to WDR, they reported respiratory irritation. Four were taken to the hospital, though only one had to remain under observation because of an injury.

Microsoft has since resolved the outage. Its status page no longer lists any problems and directs visitors to earlier updates shared on Twitter/X. In those posts, Microsoft said the fix was completed on the morning of November 14, European time. The outage highlighted how dependent parts of everyday life have become on Microsoft's infrastructure. The pool incident also raises the question of why such a critical monitoring function relies on a comparatively unreliable medium like email.