AVR Freaks

The project runs automatically. I need it to run by the user using keypad. When the project detects gas and turn on the red LED, the keypad will allow the user to turn the buzzer off and set the project to normal which is the green LED.

Thanks JC

guys can someone tell me what the following code would do? I'm trying to make the program detect the gas level. When it's higher than (400), it will turn on the red LED and the buzzer, but it will not go back to normal (green LED) until key (1) in the keypad is pressed. Unfortunately, I'm getting different result. Please guide me through this. 

// include the library code:
#include <LiquidCrystal.h>
#include <Keypad.h>
// connected to the output pin of MQ-X
int mqx_analogPin = A0; 
int redLed = 7;
int greenLed = 6;
int buzzer = 7;

int row3=A1;
int row2=A2;
int row1=A3;
int row0=A4;

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

//Keypad init
const byte numRows= 4;
const byte numCols= 4;
char keymap[numRows][numCols]= { {'1', '2', '3', 'A'},
                                 {'4', '5', '6', 'B'},
                                 {'7', '8', '9', 'C'},
                                 {'*', '0', '#', 'D'} };
                                 
byte rowPins[numRows] = {row0,row1,row2,row3};      //Rows    0 to 3
byte colPins[numCols]= {13,10,9,8};                //Columns 0 to 3


//initializes an instance of the Keypad class
Keypad myKeypad= Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols);

void setup(){
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  pinMode(redLed, OUTPUT);
  pinMode(greenLed, OUTPUT);
  pinMode(buzzer, OUTPUT);

   
  // Print a message to the LCD.
  lcd.print("Smoke Sensor");

  digitalWrite(redLed, LOW);
  digitalWrite(greenLed, HIGH);
  //buzzer off
  noTone(buzzer);
  
}
void loop()
{
  //initiallize float variable to store value from sensor (analog value from A0)
  float mqx_value = analogRead(mqx_analogPin);
//  mqx_value= mqx_value*9.775;       // i.e 10000ppm/1023 adc bits
  //set the curser starting address of LCD where we want to print sensor value 
  lcd.setCursor(0, 1);

  //print sensor value on lcd
  lcd.print(mqx_value);

  // buzer thereshhold you can set it according to the sensitivity
  if(mqx_value > 400) 
  {
    digitalWrite(redLed, HIGH);
    digitalWrite(greenLed, LOW);
    //buzzer on
    tone(buzzer, 1000);
  }

char keypressed = myKeypad.getKey();
if ( keypressed)

{


//Serial.print(keypressed);
 
 lcd.clear();
 lcd.setCursor(0, 0);
 lcd.print("Pressed ");
 // lcd.setCursor(1, 1);
 lcd.print(keypressed);

 if(keypressed=='1'){
     digitalWrite(redLed, LOW);
     digitalWrite(greenLed, HIGH);
    //buzzer off
    noTone(buzzer);
    }

 delay(1000);
 
} 
//  Just here to slow down the output.
//  delay(1000);  
}