trapped in the dpf the dpf module 120 may be regenerated through known regeneration techniques these techniques may involve controlling one or more of the temperature of the fluid the pressure of the fluid and the proportion of unburnt fuel in the fluid at this point in the apparatus exhaust fluid may pass from the dpf module 120 into the first end coupling 15 where it flows past the injector module 16 the injector module 16 may be associated with or attachable to a pump electronic tank unit petu the pump electronic tank unit may comprise a tank for providing a reservoir for emissions fluid to be injected by the injector such emissions fluids may include urea or ammonia the petu may further comprise a controller configured to control a volume of emissions fluid to be injected from the tank by the injector the controller may have as inputs for example temperature information and quantity of no x information which may be derived from sensors in the scr module 140 emissions fluid may pass from the injector module 16 into the mixer module not shown located in the second conduit 20 the mixer module may comprise features for ensuring that the exhaust fluid originating from the first conduit 10 is well mixed with the emissions fluid originating from the injector 16 to create a mixed fluid the mixed fluid may pass from the second conduit 20 and into the scr module located in the first portion of the third conduit via the second end coupling 25 the scr module 140 may comprise one or.