diff --git a/caimira/apps/calculator/static/js/co2_form.js b/caimira/apps/calculator/static/js/co2_form.js
index 4618263c..c87739ef 100644
--- a/caimira/apps/calculator/static/js/co2_form.js
+++ b/caimira/apps/calculator/static/js/co2_form.js
@@ -1,245 +1,357 @@
 const CO2_data_form = [
-	'CO2_data',
-	'exposed_coffee_break_option',
-	'exposed_coffee_duration',
-	'exposed_finish',
-	'exposed_lunch_finish',
-	'exposed_lunch_option',
-	'exposed_lunch_start',
-	'exposed_start',
-	'fitting_ventilation_states',
-	'fitting_ventilation_type',
-	'infected_coffee_break_option',
-	'infected_coffee_duration',
-	'infected_dont_have_breaks_with_exposed',
-	'infected_finish',
-	'infected_lunch_finish',
-	'infected_lunch_option',
-	'infected_lunch_start',
-	'infected_people',
-	'infected_start',
-	'room_volume',
-	'total_people',
-	'ventilation_type',
-  ];
-  
-  // Method to upload a valid excel file
-  function uploadFile(endpoint) {
-	clearFittingResultComponent();
-	const files = $("#file_upload")[0].files;
-	if (files.length === 0) {
-		$("#upload-error").show();
-	  return;
-	} else {
-		$("#upload-error").hide();
-	};
-	const file = files[0];
-	const extension = file.name.substring(file.name.lastIndexOf(".")).toUpperCase();
-	extension === ".XLS" || extension === ".XLSX"
-	  ? excelFileToJSON(endpoint, file)
-	  : $('#upload-file-extention-error').show();
+  "CO2_data",
+  "exposed_coffee_break_option",
+  "exposed_coffee_duration",
+  "exposed_finish",
+  "exposed_lunch_finish",
+  "exposed_lunch_option",
+  "exposed_lunch_start",
+  "exposed_start",
+  "fitting_ventilation_states",
+  "fitting_ventilation_type",
+  "infected_coffee_break_option",
+  "infected_coffee_duration",
+  "infected_dont_have_breaks_with_exposed",
+  "infected_finish",
+  "infected_lunch_finish",
+  "infected_lunch_option",
+  "infected_lunch_start",
+  "infected_people",
+  "infected_start",
+  "room_volume",
+  "total_people",
+  "ventilation_type",
+];
+
+// Method to upload a valid excel file
+function uploadFile(endpoint) {
+  clearFittingResultComponent();
+  const files = $("#file_upload")[0].files;
+  if (files.length === 0) {
+    $("#upload-error").show();
+    return;
   }
-  
-  // Method to read excel file and convert it into JSON
-  function excelFileToJSON(endpoint, file) {
-	try {
-	  const reader = new FileReader();
-	  reader.readAsBinaryString(file);
-	  reader.onload = function (e) {
-		const data = e.target.result;
-		const workbook = XLSX.read(data, { type: "binary" });
-		const firstSheetName = workbook.SheetNames[0];
-		const jsonData = XLSX.utils.sheet_to_json(workbook.Sheets[firstSheetName]);
-		displayJsonToHtmlTable(endpoint, jsonData);
-	  };
-	} catch (e) {
-	  console.error(e);
-	}
+  const file = files[0];
+  const extension = file.name
+    .substring(file.name.lastIndexOf("."))
+    .toUpperCase();
+  if (extension !== ".XLS" && extension !== ".XLSX") {
+    $("#upload-error")
+      .text("Please select a valid excel file (.XLS or .XLSX).")
+      .show();
+    return;
   }
-  
-  // Method to display the data in HTML Table
-  function displayJsonToHtmlTable(endpoint, jsonData) {
-	// const table = $("#display_excel_data");
-	const format = $("#CO2_data");
-	const structure = { times: [], CO2: [] };
-	if (jsonData.length > 0) {
-	  for (let i = 0; i < jsonData.length; i++) {
-		const row = jsonData[i];
-		structure.times.push(row["Times"]);
-		structure.CO2.push(row["CO2"]);
-	  }
-	  format.val(JSON.stringify(structure));
-	  $('#generate_fitting_data').prop("disabled", false);
-	  $('#fitting_ventilation_states').prop('disabled', false);
-	  $('[name=fitting_ventilation_type]').prop('disabled', false);
-	  plotCO2Data(endpoint);
-	}; 
+
+  // FileReader API to read the Excel file
+  const reader = new FileReader();
+  reader.onload = function (event) {
+    const fileContent = event.target.result;
+    const workbook = XLSX.read(fileContent, { type: "binary" });
+
+    // Assuming the first sheet is the one we want to validate
+    const firstSheetName = workbook.SheetNames[0];
+    const worksheet = workbook.Sheets[firstSheetName];
+
+    // Check if the headers match the expected format
+    const headerCoordinates = {
+      Times: "A1",
+      CO2: "B1",
+    };
+    for (const header in headerCoordinates) {
+      const cellValue = worksheet[headerCoordinates[header]]?.v;
+      if (
+        !cellValue ||
+        cellValue.trim().toLowerCase() !== header.toLowerCase()
+      ) {
+        $("#upload-error")
+          .text(`The file does not have the expected header "${header}".`)
+          .show();
+        return;
+      }
+    }
+
+    // Check if there is any data below the header row
+    if (data.length <= 1) {
+      $("#upload-error")
+        .text(
+          "The Excel file is empty. Please make sure it contains data below the header row."
+        )
+        .show();
+      return;
+    }
+
+    // Validate data in the columns
+    const data = XLSX.utils.sheet_to_json(worksheet, { header: 1, raw: false });
+    const timesColumnIndex = 0;
+    const CO2ColumnIndex = 1;
+    for (let i = 1; i < data.length; i++) {
+      try {
+        const timesCellValue = parseFloat(data[i][timesColumnIndex]);
+        const CO2CellValue = parseFloat(data[i][CO2ColumnIndex]);
+
+        if (isNaN(timesCellValue) || isNaN(CO2CellValue)) {
+          throw new Error("Invalid data in the Times or CO2 columns.");
+        }
+      } catch (error) {
+        $("#upload-error")
+          .text(
+            "Invalid data in the Times or CO2 columns. Please make sure they contain only float values."
+          )
+          .show();
+        return;
+      }
+    }
+
+    // Call function to convert Excel file to JSON and further processing
+    try {
+      generateJSONStructure(endpoint, data);
+      // If all validations pass, process the file here or display a success message
+      $("#upload-file-extention-error").hide();
+    } catch (error) {
+      console.log(error);
+    }
+  };
+  reader.readAsBinaryString(file); // Read the file as a binary string
+}
+
+// Method to generate the JSON structure
+function generateJSONStructure(endpoint, jsonData) {
+  const inputToPopulate = $("#CO2_data");
+
+  // Initialize the final structure
+  const finalStructure = { times: [], CO2: [] };
+
+  if (jsonData.length > 0) {
+    // Loop through the input dataArray and extract the values starting from the second array (index 1)
+    for (let i = 1; i < jsonData.length; i++) {
+      const arr = jsonData[i];
+      // Assuming arr contains two float values
+      finalStructure.times.push(parseFloat(arr[0]));
+      finalStructure.CO2.push(parseFloat(arr[1]));
+    }
+    inputToPopulate.val(JSON.stringify(finalStructure));
+    $("#generate_fitting_data").prop("disabled", false);
+    $("#fitting_ventilation_states").prop("disabled", false);
+    $("[name=fitting_ventilation_type]").prop("disabled", false);
+    plotCO2Data(endpoint);
   }
-  
-  // Method to download Excel template available on CERNBox
-  function downloadTemplate(uri = 'https://caimira-resources.web.cern.ch/CO2_template.xlsx', filename = 'CO2_template.xlsx') {
-	const link = document.createElement("a");
-	link.download = filename;
-	link.href = uri;
-	document.body.appendChild(link);
-	link.click();
-	document.body.removeChild(link);
-	delete link;
+}
+
+// Method to download Excel template available on CERNBox
+function downloadTemplate(
+  uri = "https://caimira-resources.web.cern.ch/CO2_template.xlsx",
+  filename = "CO2_template.xlsx"
+) {
+  const link = document.createElement("a");
+  link.download = filename;
+  link.href = uri;
+  document.body.appendChild(link);
+  link.click();
+  document.body.removeChild(link);
+  delete link;
+}
+
+function insertErrorFor(referenceNode, text) {
+  const element = $("<span></span>")
+    .addClass("error_text text-danger")
+    .html("&nbsp;&nbsp;" + text);
+  $(referenceNode).before(element);
+}
+
+function validateFormInputs(obj) {
+  $("span.error_text").remove();
+  let submit = true;
+  for (let i = 0; i < CO2_data_form.length; i++) {
+    const element = $(`[name=${CO2_data_form[i]}]`)[0];
+    if (element.name !== "fitting_ventilation_states" && element.value === "") {
+      insertErrorFor(
+        $("#DIVCO2_data_dialog"),
+        `'${element.name}' must be defined.<br />`
+      );
+      submit = false;
+    }
   }
-  
-  function insertErrorFor(referenceNode, text) {
-	const element = $('<span></span>').addClass('error_text text-danger').html('&nbsp;&nbsp;' + text);
-	$(referenceNode).before(element);
+  if (submit) {
+    $($(obj).data("target")).modal("show");
+    $("#upload-error").hide();
+    $("#upload-file-extention-error").hide();
   }
-  
-  function validateFormInputs(obj) {
-	$('span.error_text').remove();
-	let submit = true;
-	for (let i = 0; i < CO2_data_form.length; i++) {
-	  const element = $(`[name=${CO2_data_form[i]}]`)[0];
-	  if (element.name !== 'fitting_ventilation_states' && element.value === '') {
-		insertErrorFor($('#DIVCO2_data_dialog'), `'${element.name}' must be defined.<br />`);
-		submit = false;
-	  }
-	}
-	if (submit) {
-	  $($(obj).data('target')).modal('show');
-	  $("#upload-error").hide();
-	  $('#upload-file-extention-error').hide();
-	}
-	return submit;
-  }  
+  return submit;
+}
 
 function validateCO2Form() {
-	let submit = true;
-	if (validateFormInputs($('#button_fit_data'))) submit = true;
-	
-	// Check if natural ventilation is selected
-	if ($('input[name="fitting_ventilation_type"]:checked')[0].value == 'fitting_natural_ventilation') {
-		// Validate ventilation scheme
-		const element = $('[name=fitting_ventilation_states')[0]
-		if (element.value !== '') {
-			// validate input format
-			try {
-				const parsedValue = JSON.parse(element.value);
-          		if (!Array.isArray(parsedValue)) {
-					insertErrorFor($('#DIVCO2_fitting_result'), `'${element.name}' must be a list.</br>`);
-					submit = false;
-				};
-			} catch {
-				insertErrorFor($('#DIVCO2_fitting_result'), `'${element.name}' must be a list of numbers.</br>`);
-				submit = false;
-			};
-		} else {
-			insertErrorFor($('#DIVCO2_fitting_result'), `'${element.name}' must be defined.</br>`);
-			submit = false;
-		};
-	};
+  let submit = true;
+  if (validateFormInputs($("#button_fit_data"))) submit = true;
 
-	return submit;
+  // Check if natural ventilation is selected
+  if (
+    $('input[name="fitting_ventilation_type"]:checked')[0].value ==
+    "fitting_natural_ventilation"
+  ) {
+    // Validate ventilation scheme
+    const element = $("[name=fitting_ventilation_states")[0];
+    if (element.value !== "") {
+      // validate input format
+      try {
+        const parsedValue = JSON.parse(element.value);
+        if (!Array.isArray(parsedValue)) {
+          insertErrorFor(
+            $("#DIVCO2_fitting_result"),
+            `'${element.name}' must be a list.</br>`
+          );
+          submit = false;
+        }
+      } catch {
+        insertErrorFor(
+          $("#DIVCO2_fitting_result"),
+          `'${element.name}' must be a list of numbers.</br>`
+        );
+        submit = false;
+      }
+    } else {
+      insertErrorFor(
+        $("#DIVCO2_fitting_result"),
+        `'${element.name}' must be defined.</br>`
+      );
+      submit = false;
+    }
+  }
+
+  return submit;
 }
 
 function displayTransitionTimesHourFormat(start, stop) {
-	var minutes_start = (start % 1 * 60).toPrecision(2);
-	var minutes_stop = (stop % 1 * 60).toPrecision(2);
-	return Math.floor(start) + ':' + ((minutes_start != '0.0') ? minutes_start : '00') + ' - ' + Math.floor(stop) + ':' + ((minutes_stop != '0.0') ? minutes_stop : '00');
+  var minutes_start = ((start % 1) * 60).toPrecision(2);
+  var minutes_stop = ((stop % 1) * 60).toPrecision(2);
+  return (
+    Math.floor(start) +
+    ":" +
+    (minutes_start != "0.0" ? minutes_start : "00") +
+    " - " +
+    Math.floor(stop) +
+    ":" +
+    (minutes_stop != "0.0" ? minutes_stop : "00")
+  );
 }
 
 function displayFittingData(json_response) {
-	$("#DIVCO2_fitting_result").show();
-	$("#CO2_data_plot").attr("src", json_response['CO2_plot']);
-	// Not needed for the form submission
-	delete json_response['CO2_plot']; 
-	$("#CO2_fitting_result").val(JSON.stringify(json_response));
-	$("#exhalation_rate_fit").html('Exhalation rate: ' + String(json_response['exhalation_rate'].toFixed(2)) + ' m³/h');
-	let ventilation_table = "<tr><th>Time (HH:MM)</th><th>ACH value (h⁻¹)</th></tr>";
-	json_response['ventilation_values'].forEach((val, index) => {
-		let transition_times = displayTransitionTimesHourFormat(json_response['transition_times'][index], json_response['transition_times'][index + 1]);
-		ventilation_table += `<tr><td>${transition_times}</td><td>${val.toPrecision(2)}</td></tr>`;
-	});
-	$('#disable_fitting_algorithm').prop('disabled', false);
-	$("#ventilation_rate_fit").html(ventilation_table);
-	$("#generate_fitting_data").html('Fit data');
-	$("#generate_fitting_data").hide();
-	$("#save_and_dismiss_dialog").show();
+  $("#DIVCO2_fitting_result").show();
+  $("#CO2_data_plot").attr("src", json_response["CO2_plot"]);
+  // Not needed for the form submission
+  delete json_response["CO2_plot"];
+  $("#CO2_fitting_result").val(JSON.stringify(json_response));
+  $("#exhalation_rate_fit").html(
+    "Exhalation rate: " +
+      String(json_response["exhalation_rate"].toFixed(2)) +
+      " m³/h"
+  );
+  let ventilation_table =
+    "<tr><th>Time (HH:MM)</th><th>ACH value (h⁻¹)</th></tr>";
+  json_response["ventilation_values"].forEach((val, index) => {
+    let transition_times = displayTransitionTimesHourFormat(
+      json_response["transition_times"][index],
+      json_response["transition_times"][index + 1]
+    );
+    ventilation_table += `<tr><td>${transition_times}</td><td>${val.toPrecision(
+      2
+    )}</td></tr>`;
+  });
+  $("#disable_fitting_algorithm").prop("disabled", false);
+  $("#ventilation_rate_fit").html(ventilation_table);
+  $("#generate_fitting_data").html("Fit data");
+  $("#generate_fitting_data").hide();
+  $("#save_and_dismiss_dialog").show();
 }
 
 function formatCO2DataForm(CO2_data_form) {
-	let CO2_mapping = {};
-	CO2_data_form.map(el => {
-		let element = $(`[name=${el}]`);
-		// Validate checkboxes
-		if (element[0].type == 'checkbox') {
-			CO2_mapping[element[0].name] = String(+element[0].checked);
-		}
-		// Validate radio buttons
-		else if (element[0].type == 'radio') CO2_mapping[element[0].name] = $(`[name=${element[0].name}]:checked`)[0].value;
-		else CO2_mapping[element[0].name] = element[0].value;
-	});
-	return CO2_mapping;
+  let CO2_mapping = {};
+  CO2_data_form.map((el) => {
+    let element = $(`[name=${el}]`);
+    // Validate checkboxes
+    if (element[0].type == "checkbox") {
+      CO2_mapping[element[0].name] = String(+element[0].checked);
+    }
+    // Validate radio buttons
+    else if (element[0].type == "radio")
+      CO2_mapping[element[0].name] = $(
+        `[name=${element[0].name}]:checked`
+      )[0].value;
+    else CO2_mapping[element[0].name] = element[0].value;
+  });
+  return CO2_mapping;
 }
 
 function plotCO2Data(url) {
-	if (validateFormInputs()) {
-		let CO2_mapping = formatCO2DataForm(CO2_data_form);
-		fetch(url, {
-			method: "POST",
-			body: JSON.stringify(CO2_mapping),
-		})
-			.then((response) => 
-				response.json()
-					.then(json_response => $("#CO2_data_plot").attr("src", json_response['CO2_plot']))
-					.then($('#DIVCO2_fitting_to_submit').show())
-					.catch(error => console.log(error))
-			);
-	}
+  if (validateFormInputs()) {
+    let CO2_mapping = formatCO2DataForm(CO2_data_form);
+    fetch(url, {
+      method: "POST",
+      body: JSON.stringify(CO2_mapping),
+    }).then((response) =>
+      response
+        .json()
+        .then((json_response) =>
+          $("#CO2_data_plot").attr("src", json_response["CO2_plot"])
+        )
+        .then($("#DIVCO2_fitting_to_submit").show())
+        .catch((error) => console.log(error))
+    );
+  }
 }
 
 function submitFittingAlgorithm(url) {
-	if (validateCO2Form()) {
-	  // Disable all the ventilation inputs
-	  $('#fitting_ventilation_states, [name=fitting_ventilation_type]').prop('disabled', true);
-  
-	  // Prepare data for submission
-	  const CO2_mapping = formatCO2DataForm(CO2_data_form);
-	  $('#CO2_input_data_div').show();
-	  $('#disable_fitting_algorithm').prop('disabled', true);
-	  $('#generate_fitting_data')
-		.html('<span id="loading_spinner" class="spinner-border spinner-border-sm mr-2" role="status" aria-hidden="true"></span>Loading...')
-		.prop('disabled', true);
-	  $('#CO2_input_data').html(JSON.stringify(CO2_mapping, null, '\t'));
-  
-	  fetch(url, {
-		method: 'POST',
-		body: JSON.stringify(CO2_mapping),
-	  })
-		.then((response) => response.json())
-		.then((json_response) => {
-		  displayFittingData(json_response);
-		});
-	}
-  }
-  
-  function clearFittingResultComponent() {
-	// Remove all the previously generated fitting elements
-	$('#generate_fitting_data').prop('disabled', true);
-	$('#CO2_fitting_result').val('');
-	$('#CO2_data').val('{}');
-	$('#fitting_ventilation_states').val('');
-	$('span.error_text').remove();
-	$('#DIVCO2_fitting_result, #CO2_input_data_div').hide();
-	$('#DIVCO2_fitting_to_submit').hide();
-	$('#CO2_data_plot').attr('src', '');
-  
-	// Update the ventilation scheme components
-	$('#fitting_ventilation_states, [name=fitting_ventilation_type]').prop('disabled', false);
-  
-	// Update the bottom right buttons
-	$('#generate_fitting_data').show();
-	$('#save_and_dismiss_dialog').hide();
-  }
-  
-  function disableFittingAlgorithm() {
-	clearFittingResultComponent();
-	$('#CO2_data_no').click();
+  if (validateCO2Form()) {
+    // Disable all the ventilation inputs
+    $("#fitting_ventilation_states, [name=fitting_ventilation_type]").prop(
+      "disabled",
+      true
+    );
+
+    // Prepare data for submission
+    const CO2_mapping = formatCO2DataForm(CO2_data_form);
+    $("#CO2_input_data_div").show();
+    $("#disable_fitting_algorithm").prop("disabled", true);
+    $("#generate_fitting_data")
+      .html(
+        '<span id="loading_spinner" class="spinner-border spinner-border-sm mr-2" role="status" aria-hidden="true"></span>Loading...'
+      )
+      .prop("disabled", true);
+    $("#CO2_input_data").html(JSON.stringify(CO2_mapping, null, "\t"));
+
+    fetch(url, {
+      method: "POST",
+      body: JSON.stringify(CO2_mapping),
+    })
+      .then((response) => response.json())
+      .then((json_response) => {
+        displayFittingData(json_response);
+      });
   }
+}
+
+function clearFittingResultComponent() {
+  // Remove all the previously generated fitting elements
+  $("#generate_fitting_data").prop("disabled", true);
+  $("#CO2_fitting_result").val("");
+  $("#CO2_data").val("{}");
+  $("#fitting_ventilation_states").val("");
+  $("span.error_text").remove();
+  $("#DIVCO2_fitting_result, #CO2_input_data_div").hide();
+  $("#DIVCO2_fitting_to_submit").hide();
+  $("#CO2_data_plot").attr("src", "");
+
+  // Update the ventilation scheme components
+  $("#fitting_ventilation_states, [name=fitting_ventilation_type]").prop(
+    "disabled",
+    false
+  );
+
+  // Update the bottom right buttons
+  $("#generate_fitting_data").show();
+  $("#save_and_dismiss_dialog").hide();
+}
+
+function disableFittingAlgorithm() {
+  clearFittingResultComponent();
+  $("#CO2_data_no").click();
+}
diff --git a/caimira/apps/templates/base/calculator.form.html.j2 b/caimira/apps/templates/base/calculator.form.html.j2
index 91be606c..7b7d0d6b 100644
--- a/caimira/apps/templates/base/calculator.form.html.j2
+++ b/caimira/apps/templates/base/calculator.form.html.j2
@@ -330,8 +330,7 @@
               <!-- Input element to upload an excel file -->
               <input type="file" id="file_upload" />
               <button type="button" class="btn btn-primary btn-sm" onclick="uploadFile('{{ get_calculator_url() }}/co2-fit/plot');">Upload</button>  
-              <div id="upload-error" class="mb-0 mt-2 alert alert-danger" style="display: none" role="alert">Please choose any file...</div>
-              <div id="upload-file-extention-error" class="mb-0 mt-2 alert alert-danger" style="display: none" role="alert">Please select a valid excel file.</div>
+              <div id="upload-error" class="mb-0 mt-2 alert alert-danger" style="display: none" role="alert"></div>
               <br>
               <!-- Formatted excel data -->
               <input id="CO2_data" type="text" name="CO2_data" form="not-submitted" class="form-control d-none" placeholder='{"times": [...], "concentrations": [...]}' value="{}"><br>
diff --git a/caimira/apps/templates/base/layout.html.j2 b/caimira/apps/templates/base/layout.html.j2
index 73d7637d..5ea37537 100644
--- a/caimira/apps/templates/base/layout.html.j2
+++ b/caimira/apps/templates/base/layout.html.j2
@@ -110,7 +110,10 @@
   <script src="{{ get_url('/static/js') }}/ScrollMagic.min.js"></script>
   <script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.5.3/js/bootstrap.min.js" integrity="sha512-8qmis31OQi6hIRgvkht0s6mCOittjMa9GMqtK9hes5iEQBQE/Ca6yGE5FsW36vyipGoWQswBj/QBm2JR086Rkw==" crossorigin="anonymous"></script>
   <script src="{{ get_url('/static/js') }}/usage-tracking.js"></script>
-
+  
+  <!-- SheetJS for Excel validation -->
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.16.9/xlsx.full.min.js"></script>
+  
   {% block body_scripts %}
   {% endblock body_scripts %}