Keep in mind IR thermometers are sensitive to the reflectivity/emissivity of the materials they are used on, and the shiny PEI surface can be a bit tricky. Try measuring the temperature of a mirror that your warmed up with your hand and you’ll see a similar problem.
If you want to test more accurately, put some matte tape on the bed and then measure the temperature then.
That said there is also a chance for the heat bed to be a bit lower than target temperature, since the temperature control and feedback occurs at the bottom of the bed where the thermistor is, not at the top, and is separated by a layer of magnetic adhesive and coated metal.
Ventilation is key. If you can exhaust the fumes to a window with a fan that would be ideal, and a respirator should be a secondary option. Though if you must, you need something with OV on it for organic vapours.