diff --git a/rfc3164/model.go b/rfc3164/model.go
index 0e230b4..d5e3083 100644
--- a/rfc3164/model.go
+++ b/rfc3164/model.go
@@ -25,12 +25,56 @@ func NewPRI(value byte) (PRI, error) {
 	return PRI{value: value}, nil
 }
 
+type Facility byte
+
+// Definition taken from https://datatracker.ietf.org/doc/html/rfc3164#section-4.1.1
+const (
+	FacilityKernel Facility = iota
+	FacilityUser
+	FacilityMail
+	FacilitySystem
+	FacilityAuth
+	FacilitySyslog
+	FacilityLPR
+	FacilityNews
+	FacilityUUCP
+	FacilityClock
+	FacilityAuth2
+	FacilityFTP
+	FacilityNTP
+	FacilityLogAudit
+	FacilityLogAlert
+	FacilityClock2
+	FacilityLocal0
+	FacilityLocal1
+	FacilityLocal2
+	FacilityLocal3
+	FacilityLocal4
+	FacilityLocal5
+	FacilityLocal6
+	FacilityLocal7
+)
+
 // Facility returns the facility value of the PRI.
-func (p PRI) Facility() byte {
-	return p.value & 0xF8 >> 3
+func (p PRI) Facility() Facility {
+	return Facility(p.value & 0xF8 >> 3)
 }
 
+type Severity byte
+
+// Definition taken from https://datatracker.ietf.org/doc/html/rfc3164#section-4.1.1
+const (
+	SeverityEmergency Severity = iota
+	SeverityAlert
+	SeverityCritical
+	SeverityError
+	SeverityWarning
+	SeverityNotice
+	SeverityInformational
+	SeverityDebug
+)
+
 // Severity returns the severity value of the PRI.
-func (p PRI) Severity() byte {
-	return p.value & 0x07
+func (p PRI) Severity() Severity {
+	return Severity(p.value & 0x07)
 }
diff --git a/rfc5424/model.go b/rfc5424/model.go
index 8aeb6be..0d82aaa 100644
--- a/rfc5424/model.go
+++ b/rfc5424/model.go
@@ -28,14 +28,58 @@ func NewPRI(value byte) (PRI, error) {
 	return PRI{value: value}, nil
 }
 
+type Facility byte
+
+// Definition taken from https://datatracker.ietf.org/doc/html/rfc5424#section-6.2.1
+const (
+	FacilityKernel Facility = iota
+	FacilityUser
+	FacilityMail
+	FacilitySystem
+	FacilityAuth
+	FacilitySyslog
+	FacilityLPR
+	FacilityNews
+	FacilityUUCP
+	FacilityClock
+	FacilityAuth2
+	FacilityFTP
+	FacilityNTP
+	FacilityLogAudit
+	FacilityLogAlert
+	FacilityClock2
+	FacilityLocal0
+	FacilityLocal1
+	FacilityLocal2
+	FacilityLocal3
+	FacilityLocal4
+	FacilityLocal5
+	FacilityLocal6
+	FacilityLocal7
+)
+
 // Facility returns the facility value of the PRI.
-func (p PRI) Facility() byte {
-	return p.value & 0xF8 >> 3
+func (p PRI) Facility() Facility {
+	return Facility(p.value & 0xF8 >> 3)
 }
 
+type Severity byte
+
+// Definition taken from https://datatracker.ietf.org/doc/html/rfc5424#section-6.2.1
+const (
+	SeverityEmergency Severity = iota
+	SeverityAlert
+	SeverityCritical
+	SeverityError
+	SeverityWarning
+	SeverityNotice
+	SeverityInformational
+	SeverityDebug
+)
+
 // Severity returns the severity value of the PRI.
-func (p PRI) Severity() byte {
-	return p.value & 0x07
+func (p PRI) Severity() Severity {
+	return Severity(p.value & 0x07)
 }
 
 // StructuredDataElement represents a structured data element in a syslog message.