packetXBee* paq_sent;
int8_t state=0;
long previous=0;
char aux[200];
char* macHigh="          ";
char* macLow="           ";
int aux_1 = 0;
int aux_2 = 0;

// Set resistor here
#define CO_GAIN 1
#define CO_RESISTOR 0.5
#define CO2_GAIN 14
#define O2_GAIN 1
#define O3_GAIN 1
#define O3_RESISTOR 0.5
#define ACS1_GAIN 1
#define ACS1_RESISTOR 0.5
#define ACS2_GAIN 1
#define ACS2_RESISTOR 0.5

float value_Air=0.0;
float value_T=0.0;
float value_CO=0.0;
float value_CO2=0.0;
float value_O2=0.0;
float value_O3=0.0;
float value_ACS1=0.0;
float value_ACS2=0.0;


#define key_access "LIBELIUM"

uint8_t batt;
uint8_t direction[8]={0x00,0x00,0x00,0x00,0x00,0x00,0xFF,0xFF};

void setup(){

  // Store key access in EEPROM
  for(int i=0;i<8;i++){
    Utils.writeEEPROM(i+107,key_access[i]);
  }

  XBee.setMode(XBEE_ON);
  XBee.begin(9600);
  delay(1000);
  XBee.print("+++");
  delay(2000);
  XBee.println("ATBD5,AP2,WR,CN");
  delay(150);
 
  XBee.setMode(XBEE_OFF);
  XBee.close();
   
  Utils.setLED(LED0, LED_ON);
  Utils.setLED(LED1, LED_ON);
  delay(5000);
  Utils.setLED(LED0, LED_OFF);
  Utils.setLED(LED1, LED_OFF);
  for (int i=0;i<24;i++){
    Utils.blinkLEDs(125);
  }
 
  // Inits the XBee XSC library
  xbeeZB.init(ZIGBEE,FREQ2_4G,NORMAL);
 
  // Powers XBee
  xbeeZB.ON();
 
  // Get the XBee MAC address

  delay(500);
 
  int counter = 0; 
  while(xbeeZB.getOwnMac()==1&&counter<4){
    xbeeZB.getOwnMac();
    counter++;
  }
 
  Utils.hex2str(xbeeZB.sourceMacHigh,macHigh,4);
  Utils.hex2str(xbeeZB.sourceMacLow,macLow,4);

// Init USB port
  USB.begin();
 
  ACC.ON();

}

void loop(){
 
  // Barometric pressure (Atmospheric Pressure Sensor; hPa – MPXAZ6115A)
 
  SensorGas.setBoardMode(SENS_ON);
  RTC.ON();
  SensorGas.setSensorMode(SENS_ON, SENS_PRESSURE);
  delay(100);
  value_Air = SensorGas.readValue(SENS_PRESSURE);
  value_Air = (value_Air - 1.25) * 1000;
  SensorGas.setSensorMode(SENS_OFF, SENS_PRESSURE);
         
  // temperature (°C)
  value_T = SensorGas.readValue(SENS_TEMPERATURE);
  value_T = (value_T - 0.5) * 100;
   
  // CO (Carbon Monoxide Sensor; ppm – Socket 3B; TGS2442)
  SensorGas.configureSensor(SENS_SOCKET3B, CO_GAIN, CO_RESISTOR);
  delay(1000);
  value_CO = 100*pow ((((5*10/ SensorGas.readValue(SENS_SOCKET3B))-10)/1101),-0.7925);
     
  // CO2 (Carbon Dioxide Sensor; ppm - Socket 1A; TGS4161)
  SensorGas.configureSensor(SENS_CO2, CO2_GAIN);
  SensorGas.setSensorMode(SENS_ON, SENS_CO2);
  delay(30000);
  value_CO2 = 350* pow (10, SensorGas.readValue(SENS_CO2));
  SensorGas.setSensorMode(SENS_OFF, SENS_CO2);
 
  // O2 (%; Socket 1B; Sensor – SK-25)
  SensorGas.configureSensor(SENS_O2, O2_GAIN);
  delay(1000);
  value_O2 = SensorGas.readValue(SENS_O2);
       
  // O3 (Socket 2B; Ozone Sensor; ppb - MiCS-2610)
  SensorGas.configureSensor(SENS_SOCKET2B, O3_GAIN, O3_RESISTOR);
  SensorGas.setSensorMode(SENS_ON, SENS_SOCKET2B);
  delay(30000);
  value_O3 = exp ((SensorGas.readValue(SENS_SOCKET2B) + 7.56)/1.86);
  SensorGas.setSensorMode(SENS_OFF, SENS_SOCKET2B);
       
  // Air Contaminants Sensor 1 (ppm; Socket 2A; TGS2600)
  SensorGas.configureSensor(SENS_SOCKET2A,ACS1_GAIN,ACS1_RESISTOR);
  SensorGas.setSensorMode(SENS_ON,SENS_SOCKET2A);
  delay(30000);
  value_ACS1 = SensorGas.readValue(SENS_SOCKET2A);
  SensorGas.setSensorMode(SENS_OFF,SENS_SOCKET2A);
     
  // Air Contaminants Sensor 2 (ppm; Socket 4A; TGS2602)
  SensorGas.configureSensor(SENS_SOCKET4A,ACS2_GAIN,ACS2_RESISTOR);
  SensorGas.setSensorMode(SENS_ON, SENS_SOCKET4A);
  delay(30000);
  value_ACS2 = SensorGas.readValue(SENS_SOCKET4A);
  SensorGas.setSensorMode(SENS_OFF, SENS_SOCKET4A);
  SensorGas.setBoardMode(SENS_OFF);
 
  batt = PWR.getBatteryLevel();
   
  delay(5000);
 
 
  XBee.println("");
  XBee.print(value_Air);
  XBee.print(",");
  XBee.print(value_T);
  XBee.print(",");
  XBee.print(value_CO);
  XBee.print(",");
  XBee.print(value_CO2);
  XBee.print(",");
  XBee.print(value_O2);
  XBee.print(",");
  XBee.print(value_O3); 
  XBee.print(",");
  XBee.print(value_ACS1);
  XBee.print(",");
  XBee.print(value_ACS2);
  XBee.print(",");
  XBee.println(batt, DEC);
 
 
 
  paq_sent=(packetXBee*) calloc(1,sizeof(packetXBee));
  paq_sent->mode=BROADCAST;
  paq_sent->MY_known=0;
  paq_sent->packetID=0x52;
  paq_sent->opt=0;
  xbeeZB.hops=0;
  xbeeZB.setOriginParams(paq_sent,MAC_TYPE);
  xbeeZB.setDestinationParams(paq_sent, direction, aux, MAC_TYPE, DATA_ABSOLUTE);
  xbeeZB.sendXBee(paq_sent);
 
  free(paq_sent);
  paq_sent = NULL;
 
  delay(1000);
}

value=((value-0.05))/(0.033); //for GAIN=100

SensorGas.setBoardMode(SENS_ON);
RTC.ON();
...
SensorGas.configureSensor(SENS_O2, 100); //GAIN=100
...
value =SensorGas.readValue(SENS_O2); //In a loop with delay(5000)
value=((value-0.05))/(0.033); //O2 for GAIN=100
USB.println(value);