Air quality from PurpleAir sensor but with EPA adjustments

epaaq.5m.php

#!/usr/bin/env php
<?php
error_reporting( 0 );

// This version uses the "EPA adjustment" for wood smoke
// since my version is really meant to be when there are fires.
// Info here: <https://cfpub.epa.gov/si/si_public_file_download.cfm?p_download_id=540979&Lab=CEMM>
// jsnell@intertext.com


// Put your nearest PurpleAir sensor ID here

$show = '4896';

$url = ( 'https://www.purpleair.com/json?show=' . $show );

// Get the sensor data via JSON
$json  = @file_get_contents( $url );
$array = json_decode( $json, true );
for ( $i = 0; $i < sizeof( $array['results'] ); $i++ ) {
	$array['results'][ $i ]['Stats'] = json_decode( $array['results'][ $i ]['Stats'], true );
}
$pm25a    = $array['results'][0]['pm2_5_cf_1'];
$pm25b    = $array['results'][1]['pm2_5_cf_1'];
$humidity = $array['results'][0]['humidity']; 
$location = $array['results'][0]['Label'];
$lat      = $array['results'][1]['Lat'];
$lon      = $array['results'][1]['Lon'];
$sensor1  = $array['results'][0]['Stats']['v2'];
$sensor1l = $array['results'][0]['Stats']['v'];
$asensor  = $array['results'][0]['Stats']['v1'];
$bsensor  = $array['results'][1]['Stats']['v1'];


$epaPM    = ( (0.52 * ( ($pm25a + $pm25b) / 2) - (.085 * $humidity) + 5.71) );

$AQI      = aqiFromPM( $epaPM );

$aAQI     = aqiFromPM( $asensor );
$bAQI     = aqiFromPM( $bsensor );

settype( $AQI, 'integer' );
settype( $aAQI, 'integer' );
settype( $bAQI, 'integer' );

if ($AQI <= 50) {

echo '🟢' . '
---
' . getAQIDescription( $AQI ) . ' (' . $AQI . getAQItrend( $sensor1, $sensor1l )  . ')|color=' . getAQIcolor( $AQI ) . '
' . $location . '|href=https://www.purpleair.com/map?opt=1/i/mAQI/a10/cC0&select=' . $show . '#11/' . $lat . '/' . $lon ;

} else {

echo ( getAQIDescription( $AQI ) . ' (' . $AQI . getAQItrend( $sensor1, $sensor1l )  . ')|color=' . getAQIcolor( $AQI ) . '
---
' . $location . '|href=https://www.purpleair.com/map?opt=1/i/mAQI/a10/cC0&select=' . $show . '#11/' . $lat . '/' . $lon );

}

// Function to get AQI number from PPM reading
function aqiFromPM( $pm ) {
	if ( is_nan( $pm ) ) {
		return '-';
	}
	if ( isset( $pm ) == false ) {
		return 'Error: No value';
	}
	if ( $pm < 0.0 ) {
		return $pm;
	}
	if ( $pm > 1000.0 ) {
		return '-';
	}
	if ( $pm > 350.5 ) {
		return calcAQI( $pm, 500.0, 401.0, 500.0, 350.5 );
	} elseif ( $pm > 250.5 ) {
		return calcAQI( $pm, 400.0, 301.0, 350.4, 250.5 );
	} elseif ( $pm > 150.5 ) {
		return calcAQI( $pm, 300.0, 201.0, 250.4, 150.5 );
	} elseif ( $pm > 55.5 ) {
		return calcAQI( $pm, 200.0, 151.0, 150.4, 55.5 );
	} elseif ( $pm > 35.5 ) {
		return calcAQI( $pm, 150.0, 101.0, 55.4, 35.5 );
	} elseif ( $pm > 12.1 ) {
		return calcAQI( $pm, 100.0, 51.0, 35.4, 12.1 );
	} elseif ( $pm >= 0.0 ) {
		return calcAQI( $pm, 50.0, 0.0, 12.0, 0.0 );
	} else {
		return '-';
	}
}

// Function that actually calculates the AQI number
function calcAQI( $Cp, $Ih, $Il, $BPh, $BPl ) {
	$a = ( $Ih - $Il );
	$b = ( $BPh - $BPl );
	$c = ( $Cp - $BPl );
	return round( ( $a / $b ) * $c + $Il );
}

// Function that gets the AQI's description
function getAQIDescription( $aqinum ) {
	if ( $aqinum >= 401 ) {
		return 'Hazardous';
	} elseif ( $aqinum >= 301 ) {
		return 'Hazardous';
	} elseif ( $aqinum >= 201 ) {
		return 'Very Unhealthy';
	} elseif ( $aqinum >= 151 ) {
		return 'Unhealthy';
	} elseif ( $aqinum >= 101 ) {
		return 'Unhealthy SG';
	} elseif ( $aqinum >= 51 ) {
		return 'Moderate';
	} elseif ( $aqinum >= 0 ) {
		return 'Good';
	} else {
		return 'Unknown';
	}
}

// Function that gets the AQI's color code
function getAQIColor( $aqinum ) {


$darkmode = shell_exec('osascript <<EOF
tell application "System Events"
	tell appearance preferences
		set theMode to dark mode
	end tell
end tell
return theMode
EOF
');
$darkmodestate = filter_var($darkmode, FILTER_VALIDATE_BOOLEAN);


if ( $darkmodestate ) {
// we are in dark mode
	if ( $aqinum >= 301 ) {
		return '#7e0023';
	} elseif ( $aqinum >= 201 ) {
		return '#8f3f97';
	} elseif ( $aqinum >= 151 ) {
		return '#ff0000';
	} elseif ( $aqinum >= 101 ) {
		return 'Orange';
	} elseif ( $aqinum >= 51 ) {
		return '#ffff00';
	} elseif ( $aqinum >= 0 ) {
		return '#00e400';
	} else {
		return '#ffffff';
	}
} else {
// we are in light mode
	if ( $aqinum >= 301 ) {
		return '#7e0023';
	} elseif ( $aqinum >= 201 ) {
		return '#8f3f97';
	} elseif ( $aqinum >= 151 ) {
		return '#ff0000';
	} elseif ( $aqinum >= 101 ) {
		return '#cf7332';
	} elseif ( $aqinum >= 51 ) {
		return '#333333';
	} elseif ( $aqinum >= 0 ) {
		return '#0c990c';
	} else {
		return '#000000';
	}
}
}


// Function that checks for the AQI trend
function getAQItrend( $average, $live ) {
	if ( ( $average - $live ) > 6 ) {
		return '↓';
	} elseif ( ( $average - $live ) < -6 ) {
		return '↑';
	} else {
		return '';
	}
}

?>