Totalizer for air pollution readings, with data on carbon dioxide, oxygen, dust

#
    public class Totalizer
    {
      private double co2;
      private double o2;
      private double dust;

      public Totalizer()
      {
        this.co2 = 0.0;
        this.o2 = 0.0;
        this.dust = 0.0;
      }
      public Totalizer(double co2, double o2, double dust)
      {
        this.co2 = co2;
        this.o2 = o2;
        this.dust = dust;
      }
      public void AddReading(double co2, double o2, double dust)
      {
        this.co2 += co2;
        this.o2 += o2;
        this.dust += dust;
      }
      public double GetCO2()
      {
        return co2;
      }
      public double GetO2()
      {
        return o2;
      }
      public double GetDust()
      {
        return dust;
      }
      public override string ToString()
      {
        return