diff --git a/monitor/system.cpp b/monitor/system.cpp
index 6e2ccfa..0447cfa 100644
--- a/monitor/system.cpp
+++ b/monitor/system.cpp
@@ -107,6 +107,9 @@
 
     if (_powerState->isPowerOn())
     {
+        // Fans could be missing on startup, so check the power off rules.
+        // Tach sensors default to functional, so they wouldn't cause a power
+        // off here.
         std::for_each(_powerOffRules.begin(), _powerOffRules.end(),
                       [this](auto& rule) {
                           rule->check(PowerRuleState::runtime, _fanHealth);