diff --git a/checks/check_snmp_synology.py b/checks/check_snmp_synology.py
index eef16c7..fba315a 100755
--- a/checks/check_snmp_synology.py
+++ b/checks/check_snmp_synology.py
@@ -8,7 +8,7 @@
     - https://easysnmp.readthedocs.io/en/latest/session_api.html
 """
 
-__version__     = '0.4.0'
+__version__     = '0.5.0'
 __author__      = 'anima'
 
 # imports
@@ -187,7 +187,7 @@ class SNMPSynologyPowerSupplyResult(nagiosplugin.Result):
 
 
 #
-# Synology [DSM & DSM UC] Returns error if system fan fails
+# Synology [DSM & DSM UC] returns error if system fan fails
 #
 class SNMPSynologyFansResource(nagiosplugin.Resource):
     def __init__(self, session) -> None:
@@ -197,7 +197,7 @@ class SNMPSynologyFansResource(nagiosplugin.Resource):
         """check fans status (normal or failed)
         
         Returns:
-            nagiosplugin.Metric: single metric element (return)
+            Generator[nagisplugin.Metric]: multiple metric elements (yield)
         """
         baseoid = '.1.3.6.1.4.1.6574.1'
         fans = dict()
@@ -242,6 +242,59 @@ class SNMPSynologyFansSummary(nagiosplugin.Summary):
         return
 
 
+#
+# Synology [DSM & DSM UC] Checks whether a new version or update of DSM is available
+#
+class SNMPSynologyFirmwareResource(nagiosplugin.Resource):
+    def __init__(self, session) -> None:
+        self.session = session
+
+    def probe(self) -> list:
+        """check if firmware update available
+        
+        Returns:
+            nagiosplugin.Metric: single metric element (return)
+        """
+        baseoid = '.1.3.6.1.4.1.6574.1'
+        oids = dict()
+        oids['version'] = '.5.3.0'
+        oids['status'] = '.5.4.0'
+        oids['model'] = '.5.1.0'
+        oids['sn'] = '.5.2.0'
+
+        result = dict()
+        for key, oid in oids.items():
+            result[key] = self.session.get(baseoid + oid).value
+        return nagiosplugin.Metric(name='status', value=result, context='firmware_context')
+
+
+class SNMPSynologyFirmwareContext(nagiosplugin.Context):
+    def __init__(self, name):
+        super().__init__(name, fmt_metric='{name} is', result_cls=SNMPSynologyFirmwareResult)
+
+    def evaluate(self, metric, resource):
+        if metric.value['status'] == '1':
+            return self.result_cls(nagiosplugin.Critical, "critical", metric)
+        elif metric.value['status'] == '2':
+            return self.result_cls(nagiosplugin.Ok, "ok", metric)
+        elif metric.value['status'] in ['3', '4']:
+            return self.result_cls(nagiosplugin.Warn, "warning", metric)
+        return self.result_cls(nagiosplugin.Unknown, "unknown", metric)
+
+
+class SNMPSynologyFirmwareResult(nagiosplugin.Result):
+    def __str__(self):
+        if self.metric.value['status'] == '1': status = 'available'
+        elif self.metric.value['status'] == '2': status = 'up2date'
+        elif self.metric.value['status'] == '3': status = 'connecting'
+        elif self.metric.value['status'] == '4': status = 'disconnected'
+        else: status = 'unknown'
+        return f'Firmware of {self.metric.value["model"]} (SN: {self.metric.value["sn"]}; Version: {self.metric.value["version"]}) is in status {status}!'
+
+
+
+
+
 #
 # Arguments
 #
@@ -266,6 +319,7 @@ def parse_args() -> argparse.Namespace:
             'systemp',
             'powersupply',
             'fans',
+            'firmware',
         ],
         help='check mode to run')
 
@@ -331,6 +385,11 @@ def main():
             SNMPSynologyFansContext(name='fan_context'),
             SNMPSynologyFansSummary())
             check.name = "Fans Status"
+        case 'firmware':
+            check = nagiosplugin.Check(SNMPSynologyFirmwareResource(session=session),
+            SNMPSynologyFirmwareContext(name='firmware_context'),
+            nagiosplugin.Summary())
+            check.name = "Firmware"
         case _:
             raise nagiosplugin.CheckError(f'Unknown check mode: {args.check_mode}')