// on top of your script
new Anti_Gas[MAX_PLAYERS];

// Onplayerconnect
Anti_Gas[playerid] = 0;

// onplayerdeaths
Anti_Gas[playerid] = 0;

// onplayerspawn
if(Anti_Gas[playerid] == 1)
{
Anti_Gas[playerid] = 0;
}

// It's your tear gas mask, i've removed the attached object (the gas mask)
CMD:buymask(playerid, params[])
{
     if(GetPlayerMoney(playerid) >= 500)
     {
       if(Anti_Gas[playerid] == 0)
         {
           Anti_Gas[playerid] = 1;
           GivePlayerMoney(playerid, - 500);
          }
        }
     return 1;
}


// OnPlayerKeyStateChange
// Tear Gas Actions by xF[4]Life
	    if(newkeys & KEY_FIRE)
         	{
            new weaponid = GetPlayerWeapon(playerid);
            new Float:x, Float:y, Float:z;
			GetPlayerPos(playerid,x,y,z);
       		for(new i = 0; i < MAX_PLAYERS; i++) {
	    if(weaponid == 17)
	     {
	     if(IsPlayerInRangeOfPoint(i,10.0, x, y, z)
              && GetPlayerState(playerid) == PLAYER_STATE_ONFOOT)
        	{
        	if(Anti_Gas[i] == 0)
        	{
	         ApplyAnimation(i, "ped", "gas_cwr", 1.0, 0, 0, 0, 0, 0);
	         GivePlayerWeapon(playerid, 17, -1);
	         }
		    }
		    }
		    }
   		 }