I have asthma, went to ER 5 hours ago where they gave me 2 doses of Albuterol Nebulizer treatments. My heart is still racing at 120’s, when should it slow?

It will likely take several hours for your heart rate to return to normal. In addition to the stress of your asthma exacerbation, the albuterol you were given causes increased heart rate, so try to relax and keep your asthma under control.