diff --git a/Exit.go b/Exit.go
index 5c92cec..8d2c5b3 100644
--- a/Exit.go
+++ b/Exit.go
@@ -19,15 +19,20 @@ func ErrorExit(err error) {
 
 // Exit returns with the given returncode and message and optional PerformanceData
 func Exit(state State, msg string) {
-	LongExit(state, msg, "")
+	LongExit(state, msg, "", nil)
 }
 
 // LongExit returns with the given returncode and message and optional PerformanceData and long message
-func LongExit(state State, msg, longMsg string) {
-	if perf := PrintPerformanceData(); perf == "" {
-		fmt.Printf("%s - %s\n%s", state.name, msg, longMsg)
+func LongExit(state State, msg, longMsg string, collection *PerformanceDataCollection) {
+	perfString := ""
+	if collection != nil {
+		perfString = collection.PrintAllPerformanceData()
+	}
+
+	if perfString == "" {
+		fmt.Printf("%s - %s\n%s", state.Name, msg, longMsg)
 	} else {
-		fmt.Printf("%s - %s|%s\n%s", state.name, msg, perf, longMsg)
+		fmt.Printf("%s - %s|%s\n%s", state.Name, msg, perfString, longMsg)
 	}
-	os.Exit(state.code)
+	os.Exit(state.Code)
 }
diff --git a/PerformanceData.go b/PerformanceData.go
index 2361a55..75c0c9a 100644
--- a/PerformanceData.go
+++ b/PerformanceData.go
@@ -7,68 +7,123 @@ import (
 	"sync"
 )
 
-type PerformanceData map[string]interface{}
+// PerformanceData is a map with string keys and any values, essentially a dictionary
+// Since its an dictionary, always add add a label
+// "label" = "health_rate"
+// "value" = 80
+// "critical" = 160
+type PerformanceData map[string]any
 
-var (
-	p      []PerformanceData = []PerformanceData{}
-	pMutex                   = &sync.Mutex{}
-)
+// This is a struct that users of the library should use.
+// They have to manage this object through functions in this file
+// Library clients should get an instance of this and keep calling its methods
+type PerformanceDataCollection struct {
+	data      []PerformanceData
+	dataMutex *sync.Mutex
+}
+
+// Returns an empty PerformanceDataCollection
+func NewPerformanceDataCollection() PerformanceDataCollection {
+	return PerformanceDataCollection{
+		data:      make([]PerformanceData, 0),
+		dataMutex: &sync.Mutex{},
+	}
+}
 
-// NewPerformanceData adds a PerformanceData object which can be expanded with further information
-func NewPerformanceData(label string, value float64) *PerformanceData {
-	return NewPerformanceDataString(label, strconv.FormatFloat(value, 'f', -1, 64))
+// Adds a new PerformanceData element to the data array
+// Use the label to get the reference to the PerformanceData later on
+func (collection *PerformanceDataCollection) AddPerformanceData(label string, value string) {
+	collection.dataMutex.Lock()
+	collection.data = append(collection.data, PerformanceData{"label": label, "value": value})
+	collection.dataMutex.Unlock()
 }
 
-// NewPerformanceDataString adds a PerformanceData object which can be expanded with further information
-func NewPerformanceDataString(label, value string) *PerformanceData {
-	pMutex.Lock()
-	p = append(p, PerformanceData{"label": label, "value": value})
-	newOne := &(p[len(p)-1])
-	pMutex.Unlock()
-	return newOne
+// Calls collection.AddPerformanceData after converting float to string
+func (collection *PerformanceDataCollection) AddPerformanceDataFloat64(label string, value float64) {
+	collection.AddPerformanceData(label, strconv.FormatFloat(value, 'f', -1, 64))
 }
 
-// Unit adds an unit string to the PerformanceData
-func (p PerformanceData) Unit(unit string) PerformanceData {
-	p["unit"] = unit
-	return p
+// Internal function to find a PerformanceData with specified label
+func (collection *PerformanceDataCollection) findPerformanceData(label string) (*PerformanceData, error) {
+	for index, pd := range collection.data {
+		if pd_label, ok := pd["label"]; ok && pd_label == label {
+			return &collection.data[index], nil
+		}
+	}
+	return nil, fmt.Errorf("no performance data with the label '%s' found", label)
+}
+
+// Adds a field called "unit" to the PerformanceData with the label
+func (collection *PerformanceDataCollection) Unit(label string, unit string) error {
+	collection.dataMutex.Lock()
+	defer collection.dataMutex.Unlock()
+	pd, err := collection.findPerformanceData(label)
+	if err != nil {
+		return err
+	}
+	(*pd)["unit"] = unit
+	return nil
 }
 
-// Warn adds the threshold to the PerformanceData
-func (p PerformanceData) Warn(warn *Threshold) PerformanceData {
-	p["warn"] = warn
-	return p
+// Adds a field called "unit" to the PerformanceData with the label
+func (collection *PerformanceDataCollection) Warn(label string, warn *Threshold) error {
+	collection.dataMutex.Lock()
+	defer collection.dataMutex.Unlock()
+	pd, err := collection.findPerformanceData(label)
+	if err != nil {
+		return err
+	}
+	(*pd)["warn"] = warn
+	return nil
 }
 
-// Crit adds the threshold to the PerformanceData
-func (p PerformanceData) Crit(crit *Threshold) PerformanceData {
-	p["crit"] = crit
-	return p
+// Adds a field called "unit" to the PerformanceData with the label
+func (collection *PerformanceDataCollection) Crit(label string, crit *Threshold) error {
+	collection.dataMutex.Lock()
+	defer collection.dataMutex.Unlock()
+	pd, err := collection.findPerformanceData(label)
+	if err != nil {
+		return err
+	}
+	(*pd)["crit"] = crit
+	return nil
 }
 
-// Min adds the float64 to the PerformanceData
-func (p PerformanceData) Min(min float64) PerformanceData {
-	p["min"] = min
-	return p
+// Adds a field called "unit" to the PerformanceData with the label
+func (collection *PerformanceDataCollection) Min(label string, min float64) error {
+	collection.dataMutex.Lock()
+	defer collection.dataMutex.Unlock()
+	pd, err := collection.findPerformanceData(label)
+	if err != nil {
+		return err
+	}
+	(*pd)["min"] = min
+	return nil
 }
 
-// Min adds the float64 to the PerformanceData
-func (p PerformanceData) Max(max float64) PerformanceData {
-	p["max"] = max
-	return p
+// Adds a field called "unit" to the PerformanceData with the label
+func (collection *PerformanceDataCollection) Max(label string, max float64) error {
+	collection.dataMutex.Lock()
+	defer collection.dataMutex.Unlock()
+	pd, err := collection.findPerformanceData(label)
+	if err != nil {
+		return err
+	}
+	(*pd)["max"] = max
+	return nil
 }
 
-// toString prints this PerformanceData
-func (p PerformanceData) toString() string {
+// internal function to print a PerformanceData
+func (pd PerformanceData) toString() string {
 	var toPrint bytes.Buffer
 
-	toPrint.WriteString(fmt.Sprintf("'%s'=%s", p["label"], p["value"]))
-	if unit, ok := p["unit"]; ok {
+	toPrint.WriteString(fmt.Sprintf("'%s'=%s", pd["label"], pd["value"]))
+	if unit, ok := pd["unit"]; ok {
 		toPrint.WriteString(unit.(string))
 	}
 	toPrint.WriteString(";")
 	addThreshold := func(key string) {
-		if value, ok := p[key]; ok && value != nil {
+		if value, ok := pd[key]; ok && value != nil {
 			if t := value.(*Threshold); t != nil {
 				toPrint.WriteString(t.input)
 			}
@@ -79,7 +134,7 @@ func (p PerformanceData) toString() string {
 	addThreshold("crit")
 
 	addFloat := func(key string) {
-		if value, ok := p[key]; ok {
+		if value, ok := pd[key]; ok {
 			toPrint.WriteString(strconv.FormatFloat(value.(float64), 'f', -1, 64))
 		}
 	}
@@ -90,14 +145,33 @@ func (p PerformanceData) toString() string {
 	return toPrint.String()
 }
 
-// PrintPerformanceData prints all PerformanceData
-func PrintPerformanceData() string {
+// Finds and prints the PerformanceData found in this collection
+func (collection *PerformanceDataCollection) PrintPerformanceData(label string) (string, error) {
+	collection.dataMutex.Lock()
+	defer collection.dataMutex.Unlock()
+	pd, err := collection.findPerformanceData(label)
+	if err != nil {
+		return "", err
+	}
+
+	return (*pd).toString(), nil
+}
+
+// Prints all PerformanceData to a string in this collection
+func (collection *PerformanceDataCollection) PrintAllPerformanceData() string {
+	collection.dataMutex.Lock()
+	defer collection.dataMutex.Unlock()
 	var toPrint bytes.Buffer
-	pMutex.Lock()
-	for _, perfData := range p {
+	for _, perfData := range collection.data {
 		toPrint.WriteString(perfData.toString())
 		toPrint.WriteString(" ")
 	}
-	pMutex.Unlock()
 	return toPrint.String()
 }
+
+// Clears all PerformanceData stored in this collection
+func (collection *PerformanceDataCollection) ClearPerformanceCollection() {
+	collection.dataMutex.Lock()
+	defer collection.dataMutex.Unlock()
+	collection.data = make([]PerformanceData, 0)
+}
diff --git a/PerformanceData_test.go b/PerformanceData_test.go
index a0d50c3..da8b566 100644
--- a/PerformanceData_test.go
+++ b/PerformanceData_test.go
@@ -1,76 +1,123 @@
 package check_x
 
 import (
-	"reflect"
 	"testing"
 )
 
 var perfdataToString = []struct {
-	f        func() PerformanceData
+	f        func() PerformanceDataCollection
 	expected string
 }{
-	{func() PerformanceData {
-		return *NewPerformanceDataString("a", "1")
+	{func() PerformanceDataCollection {
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceData("a", "1")
+		return col
 	}, "'a'=1;;;;"},
-	{func() PerformanceData {
+	{func() PerformanceDataCollection {
 		warn, _ := NewThreshold("10:")
-		return NewPerformanceDataString("a", "2").Warn(warn)
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceData("a", "2")
+		col.Warn("a", warn)
+		return col
 	}, "'a'=2;10:;;;"},
-	{func() PerformanceData {
+	{func() PerformanceDataCollection {
 		warn, _ := NewThreshold("10:")
 		crit, _ := NewThreshold("@10:20")
-		return NewPerformanceDataString("a", "3").Warn(warn).Crit(crit)
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceData("a", "3")
+		col.Warn("a", warn)
+		col.Crit("a", crit)
+		return col
 	}, "'a'=3;10:;@10:20;;"},
-	{func() PerformanceData {
+	{func() PerformanceDataCollection {
 		warn, _ := NewThreshold("10:")
 		crit, _ := NewThreshold("@10:20")
-		return NewPerformanceDataString("a", "3").Warn(warn).Crit(crit).Min(0)
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceData("a", "3")
+		col.Warn("a", warn)
+		col.Crit("a", crit)
+		col.Min("a", 0)
+		return col
 	}, "'a'=3;10:;@10:20;0;"},
-	{func() PerformanceData {
+	{func() PerformanceDataCollection {
 		warn, _ := NewThreshold("10:")
 		crit, _ := NewThreshold("@10:20")
-		return NewPerformanceDataString("a", "4").Warn(warn).Crit(crit).Min(0).Max(100)
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceData("a", "4")
+		col.Warn("a", warn)
+		col.Crit("a", crit)
+		col.Min("a", 0)
+		col.Max("a", 100)
+		return col
 	}, "'a'=4;10:;@10:20;0;100"},
-	{func() PerformanceData {
+	{func() PerformanceDataCollection {
 		warn, _ := NewThreshold("10:")
 		crit, _ := NewThreshold("@10:20")
-		return NewPerformanceDataString("a", "5").Warn(warn).Crit(crit).Min(0).Max(100).Unit("C")
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceData("a", "5")
+		col.Warn("a", warn)
+		col.Crit("a", crit)
+		col.Min("a", 0)
+		col.Max("a", 100)
+		col.Unit("a", "C")
+		return col
 	}, "'a'=5C;10:;@10:20;0;100"},
-	{func() PerformanceData {
+	{func() PerformanceDataCollection {
 		warn, _ := NewThreshold("10:")
 		crit, _ := NewThreshold("@10:20")
-		return NewPerformanceData("a", 6).Warn(warn).Crit(crit).Min(0).Max(100).Unit("C")
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceDataFloat64("a", 6)
+		col.Warn("a", warn)
+		col.Crit("a", crit)
+		col.Min("a", 0)
+		col.Max("a", 100)
+		col.Unit("a", "C")
+		return col
 	}, "'a'=6C;10:;@10:20;0;100"},
-	{func() PerformanceData {
+	{func() PerformanceDataCollection {
 		warn, _ := NewThreshold("")
 		crit, _ := NewThreshold("@10:20")
-		return NewPerformanceData("a", 6).Warn(warn).Crit(crit).Min(0).Max(100).Unit("C")
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceDataFloat64("a", 6)
+		col.Warn("a", warn)
+		col.Crit("a", crit)
+		col.Min("a", 0)
+		col.Max("a", 100)
+		col.Unit("a", "C")
+		return col
 	}, "'a'=6C;;@10:20;0;100"},
-	{func() PerformanceData {
+	{func() PerformanceDataCollection {
 		crit, _ := NewThreshold("@10:20")
-		return NewPerformanceData("a", 6).Warn(nil).Crit(crit).Min(0).Max(100).Unit("C")
+		col := NewPerformanceDataCollection()
+		col.AddPerformanceDataFloat64("a", 6)
+		col.Warn("a", nil)
+		col.Crit("a", crit)
+		col.Min("a", 0)
+		col.Max("a", 100)
+		col.Unit("a", "C")
+		return col
 	}, "'a'=6C;;@10:20;0;100"},
 }
 
 func TestPerformanceData_toString(t *testing.T) {
 	for i, data := range perfdataToString {
-		result := data.f()
-		resultString := result.toString()
-		if resultString != data.expected {
-			t.Errorf("%d - Expected: %s, got: %s", i, data.expected, resultString)
+		collection := data.f()
+		collectionString, err := collection.PrintPerformanceData("a")
+		if err != nil {
+			t.Errorf("Error when finding the performance data: %s", err.Error())
 		}
-		if !reflect.DeepEqual(p[i], result) {
-			t.Errorf("%d - Expected: %s, got: %s", i, p[i], result)
+		if collectionString != data.expected {
+			t.Errorf("%d - Expected: %s, got: %s", i, data.expected, collectionString)
 		}
 	}
 }
 
 func TestPrintPerformanceData(t *testing.T) {
-	p = []PerformanceData{}
-	NewPerformanceDataString("a", "1")
-	NewPerformanceDataString("b", "2")
+	col := NewPerformanceDataCollection()
+	col.AddPerformanceData("a", "1")
+	col.AddPerformanceData("b", "2")
 	expected := "'a'=1;;;;" + " " + "'b'=2;;;; "
-	if expected != PrintPerformanceData() {
-		t.Errorf("Expected: %s, got: %s", expected, PrintPerformanceData())
+	if expected != col.PrintAllPerformanceData() {
+		t.Errorf("Expected: %s, got: %s", expected, col.PrintAllPerformanceData())
 	}
 }
diff --git a/States.go b/States.go
index eb76d6e..c45c6a1 100644
--- a/States.go
+++ b/States.go
@@ -8,8 +8,8 @@ import (
 
 // State represents an Nagioskind returncode
 type State struct {
-	name string
-	code int
+	Name string
+	Code int
 }
 
 // StateFromInt creates an known state if code is 0-3, else a new State will be returned
@@ -24,7 +24,7 @@ func StateFromInt(code int) State {
 	case 3:
 		return Unknown
 	default:
-		return State{code: code}
+		return State{Code: code}
 	}
 }
 
@@ -41,24 +41,24 @@ func StateFromString(name string) State {
 	case "unknown":
 		return Unknown
 	default:
-		return State{name: name}
+		return State{Name: name}
 	}
 }
 
 // String prints the name of the state
 func (s State) String() string {
-	return s.name
+	return s.Name
 }
 
 var (
 	// OK - returncode: 0
-	OK = State{name: "OK", code: 0}
+	OK = State{Name: "OK", Code: 0}
 	// Warning - returncode: 1
-	Warning = State{name: "WARNING", code: 1}
+	Warning = State{Name: "WARNING", Code: 1}
 	// Critical - returncode: 2
-	Critical = State{name: "CRITICAL", code: 2}
+	Critical = State{Name: "CRITICAL", Code: 2}
 	// Unknown - returncode: 3
-	Unknown = State{name: "UNKNOWN", code: 3}
+	Unknown = State{Name: "UNKNOWN", Code: 3}
 )
 
 // States is a list of state
@@ -74,7 +74,7 @@ func (s States) Len() int {
 
 // Less for Sort interface
 func (s States) Less(i, j int) bool {
-	return s[i].code < s[j].code
+	return s[i].Code < s[j].Code
 }
 
 // Swap for Sort interface
diff --git a/States_test.go b/States_test.go
index 256d3ed..d735e86 100644
--- a/States_test.go
+++ b/States_test.go
@@ -31,7 +31,7 @@ var intToState = []struct {
 	{1, Warning},
 	{2, Critical},
 	{3, Unknown},
-	{4, State{code: 4}},
+	{4, State{Code: 4}},
 }
 
 func TestStateFromInt(t *testing.T) {
@@ -50,7 +50,7 @@ var stringToState = []struct {
 	{"Warning", Warning},
 	{"Critical", Critical},
 	{"Unknown", Unknown},
-	{"FOO", State{name: "FOO"}},
+	{"FOO", State{Name: "FOO"}},
 }
 
 func TestStateFromString(t *testing.T) {