26 U.S.C. § 4053

1. (1)Any article designed—
   1. (A)to be mounted or placed on automobile trucks, automobile truck chassis, or automobile chassis, and
   2. (B)to be used primarily as living quarters or camping accommodations.
2. (2)Any body primarily designed—
   1. (A)to process or prepare seed, feed, or fertilizer for use on farms,
   2. (B)to haul feed, seed, or fertilizer to and on farms,
   3. (C)to spread feed, seed, or fertilizer on farms,
   4. (D)to load or unload feed, seed, or fertilizer on farms, or
   5. (E)for any combination of the foregoing.
3. (3)Any house trailer.
4. (4)Any ambulance, hearse, or combination ambulance-hearse.
5. (5)Any article designed—
   1. (A)to be placed or mounted on an automobile truck chassis or truck trailer or semitrailer chassis, and
   2. (B)to be used to process or prepare concrete.
6. (6)Any box, container, receptacle, bin or other similar article—
   1. (A)which is designed to be used as a trash container and is not designed for the transportation of freight other than trash, and
   2. (B)which is not designed to be permanently mounted on or permanently affixed to an automobile truck chassis or body.
7. (7)Any chassis or body of a trailer or semitrailer which is designed for use both as a highway vehicle and a railroad car. For purposes of the preceding sentence, piggy-back trailer or semitrailer shall not be treated as designed for use as a railroad car.
8. (8)Any vehicle which consists of a chassis—
   1. (A)to which there has been permanently mounted (by welding, bolting, riveting, or other means) machinery or equipment to perform a construction, manufacturing, processing, farming, mining, drilling, timbering, or similar operation if the operation of the machinery or equipment is unrelated to transportation on or off the public highways,
   2. (B)which has been specially designed to serve only as a mobile carriage and mount (and a power source, where applicable) for the particular machinery or equipment involved, whether or not such machinery or equipment is in operation, and
   3. (C)which, by reason of such special design, could not, without substantial structural modification, be used as a component of a vehicle designed to perform a function of transporting any load other than that particular machinery or equipment or similar machinery or equipment requiring such a specially designed chassis.
9. (9)Any device or system of devices which—
   1. (A)is designed to provide to a vehicle those services (such as heat, air conditioning, or electricity) that would otherwise require the operation of the main drive engine while the vehicle is temporarily parked or remains stationary using one or more devices affixed to a tractor, and
   2. (B)is determined by the Administrator of the Environmental Protection Agency, in consultation with the Secretary of Energy and the Secretary of Transportation, to reduce idling of such vehicle at a motor vehicle rest stop or other location where such vehicles are temporarily parked or remain stationary.
10. (10)Any insulation that has an R value of not less than R35 per inch.