Lift the white top of the Holmes Smoke Grabber. Lifting will release the black ashtray at the back of the device.
From the front, lift up the black ashtray and then pull out. You'll see the batteries underneath. One will be sideways on the front and the other will be on the right side of the Smoke Grabber. Carefully take these out.
Put in the new batteries, making sure you line the positive and negative sides in the appropriate positions. Replace the black ashtray, and you are ready to use your Smoke Grabber again.