Implementing two inputs in Node-RED

You will need to use a function node and make use of the context variable to keep state between messages and use the message topic to determine which input a message came from.

Something like this:

context.temp = context.temp || 0.0;
context.smoke = context.smoke || false;

if (msg.topic === 'smokeDetector') {
  context.smoke = msg.payload;
} else if (msg.topic === 'tempSensor') {
  context.temp = msg.payload;
}

if (context.temp >= 70.0 && context.smoke) {
  return {topic: 'fireState', payload: 'FIRE!'}
} else {
  return null
}

More details can be found in the function node doc here