diff --git a/PhysicsTools/NanoAOD/plugins/L1TriggerResultsConverter.cc b/PhysicsTools/NanoAOD/plugins/L1TriggerResultsConverter.cc
index 7544cfa450b8f..d2778836fd9fd 100644
--- a/PhysicsTools/NanoAOD/plugins/L1TriggerResultsConverter.cc
+++ b/PhysicsTools/NanoAOD/plugins/L1TriggerResultsConverter.cc
@@ -60,7 +60,7 @@ class L1TriggerResultsConverter : public edm::stream::EDProducer<> {
 
   // ----------member data ---------------------------
   const bool legacyL1_;
-  const bool store_unprefireable_bit_;
+  const bool store_unprefireable_bits_;
   const edm::EDGetTokenT<L1GlobalTriggerReadoutRecord> tokenLegacy_;
   const edm::EDGetTokenT<GlobalAlgBlkBxCollection> token_;
   const edm::EDGetTokenT<GlobalExtBlkBxCollection> token_ext_;
@@ -77,12 +77,12 @@ class L1TriggerResultsConverter : public edm::stream::EDProducer<> {
 //
 L1TriggerResultsConverter::L1TriggerResultsConverter(const edm::ParameterSet& params)
     : legacyL1_(params.getParameter<bool>("legacyL1")),
-      store_unprefireable_bit_(!legacyL1_ ? params.getParameter<bool>("storeUnprefireableBit") : false),
+      store_unprefireable_bits_(!legacyL1_ ? params.getParameter<bool>("storeUnprefireableBits") : false),
       tokenLegacy_(legacyL1_ ? consumes<L1GlobalTriggerReadoutRecord>(params.getParameter<edm::InputTag>("src"))
                              : edm::EDGetTokenT<L1GlobalTriggerReadoutRecord>()),
       token_(!legacyL1_ ? consumes<GlobalAlgBlkBxCollection>(params.getParameter<edm::InputTag>("src"))
                         : edm::EDGetTokenT<GlobalAlgBlkBxCollection>()),
-      token_ext_(store_unprefireable_bit_
+      token_ext_(store_unprefireable_bits_
                      ? consumes<GlobalExtBlkBxCollection>(params.getParameter<edm::InputTag>("src_ext"))
                      : edm::EDGetTokenT<GlobalExtBlkBxCollection>()),
       l1gtmenuToken_(esConsumes<edm::Transition::BeginRun>()),
@@ -117,8 +117,10 @@ void L1TriggerResultsConverter::beginRun(edm::Run const&, edm::EventSetup const&
       names_.push_back(keyval.first);
       indices_.push_back(keyval.second.getIndex());
     }
-    if (store_unprefireable_bit_)
-      names_.push_back("L1_UnprefireableEvent");
+    if (store_unprefireable_bits_) {
+      names_.push_back("L1_UnprefireableEvent_TriggerRules");
+      names_.push_back("L1_UnprefireableEvent_FirstBxInTrain");
+    }
   }
 }
 
@@ -126,20 +128,24 @@ void L1TriggerResultsConverter::beginRun(edm::Run const&, edm::EventSetup const&
 
 void L1TriggerResultsConverter::produce(edm::Event& iEvent, const edm::EventSetup& iSetup) {
   const std::vector<bool>* wordp = nullptr;
-  bool unprefireable_bit = false;
+  bool unprefireable_bit_triggerrules = false;
+  bool unprefireable_bit_firstbxintrain = false;
+
   if (!legacyL1_) {
     const auto& resultsProd = iEvent.get(token_);
     if (not resultsProd.isEmpty(0)) {
       wordp = &resultsProd.at(0, 0).getAlgoDecisionFinal();
     }
-    if (store_unprefireable_bit_) {
+    if (store_unprefireable_bits_) {
       auto handleExtResults = iEvent.getHandle(token_ext_);
       if (handleExtResults.isValid()) {
         if (not handleExtResults->isEmpty(0)) {
-          unprefireable_bit = handleExtResults->at(0, 0).getExternalDecision(GlobalExtBlk::maxExternalConditions - 1);
+          //Stores the unprefirable event decision corresponding to trigger rules (e.g.: BX0 is unprefirable because BX-3 fired and therefore BX-2/-1 are masked).
+          unprefireable_bit_triggerrules =
+              handleExtResults->at(0, 0).getExternalDecision(GlobalExtBlk::maxExternalConditions - 1);
         }
       } else {
-        LogDebug("Unprefirable bit not found, always set to false");
+        LogDebug("Unprefirable bit (trigger rules) not found, always set to false");
       }
     }
   } else {
@@ -155,9 +161,22 @@ void L1TriggerResultsConverter::produce(edm::Event& iEvent, const edm::EventSetu
     if (not mask_.empty())
       result &= (mask_.at(index) != 0);
     l1bitsAsHLTStatus[nidx] = edm::HLTPathStatus(result ? edm::hlt::Pass : edm::hlt::Fail);
+    //Stores the unprefirable event decision corresponding to events in the first bx of a train.
+    //In 2022/2023 the bx before that was manually masked.
+    //Technically this was done by enabling the L1_FirstBunchBeforeTrain bit in the L1 menu, and vetoing that bit after L1 Final OR is evaluated.
+    if (names_[nidx] == "L1_FirstBunchBeforeTrain" && !legacyL1_) {
+      const auto& resultsProd = iEvent.get(token_);
+      if (!(&resultsProd)->isEmpty(-1)) {
+        unprefireable_bit_firstbxintrain = (&resultsProd)->begin(-1)->getAlgoDecisionFinal(index);
+      }
+    }
+  }
+  if (store_unprefireable_bits_) {
+    l1bitsAsHLTStatus[indices_size] =
+        edm::HLTPathStatus(unprefireable_bit_triggerrules ? edm::hlt::Pass : edm::hlt::Fail);
+    l1bitsAsHLTStatus[indices_size + 1] =
+        edm::HLTPathStatus(unprefireable_bit_firstbxintrain ? edm::hlt::Pass : edm::hlt::Fail);
   }
-  if (store_unprefireable_bit_)
-    l1bitsAsHLTStatus[indices_size] = edm::HLTPathStatus(unprefireable_bit ? edm::hlt::Pass : edm::hlt::Fail);
   //mimic HLT trigger bits for L1
   auto out = std::make_unique<edm::TriggerResults>(l1bitsAsHLTStatus, names_);
   iEvent.put(std::move(out));
@@ -169,8 +188,8 @@ void L1TriggerResultsConverter::fillDescriptions(edm::ConfigurationDescriptions&
   desc.add<bool>("legacyL1")->setComment("is legacy L1");
   desc.add<edm::InputTag>("src")->setComment(
       "L1 input (L1GlobalTriggerReadoutRecord if legacy, GlobalAlgBlkBxCollection otherwise)");
-  desc.add<bool>("storeUnprefireableBit", false)
-      ->setComment("Activate storage of L1 unprefireable bit (needs L1 external decision input)");
+  desc.add<bool>("storeUnprefireableBits", false)
+      ->setComment("Activate storage of L1 unprefireable bits (needs L1 external decision input)");
   desc.add<edm::InputTag>("src_ext", edm::InputTag(""))
       ->setComment("L1 external decision input (GlobalExtBlkBxCollection, only supported if not legacy");
   descriptions.add("L1TriggerResultsConverter", desc);
diff --git a/PhysicsTools/NanoAOD/python/triggerObjects_cff.py b/PhysicsTools/NanoAOD/python/triggerObjects_cff.py
index 325f93f32bb14..57d77d566c28c 100644
--- a/PhysicsTools/NanoAOD/python/triggerObjects_cff.py
+++ b/PhysicsTools/NanoAOD/python/triggerObjects_cff.py
@@ -375,7 +375,7 @@ def AND(tokens):
 l1bits=cms.EDProducer("L1TriggerResultsConverter",
                        src=cms.InputTag("gtStage2Digis"),
                        legacyL1=cms.bool(False),
-                       storeUnprefireableBit=cms.bool(True),
+                       storeUnprefireableBits=cms.bool(True),
                        src_ext=cms.InputTag("simGtExtUnprefireable"))
 
 triggerObjectTablesTask = cms.Task( unpackedPatTrigger,triggerObjectTable,l1bits)