Attendance Requirements for Unloading Railcars
Pipeline and Hazardous Materials Safety Administration · Mar 24, 2000 · Reference No. 99-0185
Interprets: 49 CFR § 174.67
Reggie’s quick take
Someone asked whether a chlorine railcar unloading station could meet attendance rules without a technician standing within 25 feet of the railcar, if remote monitoring and controls were in place. PHMSA says it may, if four conditions are met. A worker must be responsible for unloading and know the material. That worker must be trained in procedures and emergencies and be able to stop the flow right away. The system must be able to halt the flow or alert that worker in an emergency. Any device malfunction must be reported immediately or checked hourly. If the device malfunctions, someone must watch the unloading constantly.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This is in response to your letter regarding attendance requirements for unloading chlorine from railcars under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). I apologize for the delay in responding and hope it has not caused any inconvenience. You provided the following scenario:
Ambar Chemical's unloading station is inside a building that is connected to an emergency caustic scrubber that has been designed to neutralize an entire railcar full of chlorine (90 tons). The railcar pressure and the valves used to isolate the railcar from the process can be remotely actuated from the bromine plant control room. There are chlorine detectors in the unloading building that transmit an alarm signal to the bromine plant control room whenever a chlorine level of 1 part per million is detected. The control room is occupied 24 hours a day. Currently, Ambar Chemical offloads chlorine only while one of the bromine plant technicians is physically within 25 feet of the railcar and can see the railcar unloading piping and valves.
You asked, provided the non-human monitoring and control systems described above meet the attendance requirements of 49 CFR 174.67(I), if it is necessary to have a plant technician physically located within 25 feet of the railcar who can see the railcar unloading piping and valves.
Under the HMR, Ambar Chemical's proposed system for non-human monitoring may meet the attendance requirements in 49 CFR 174.67(a)(1) and (I) for unloading a railcar containing chlorine provided:
1) An employee is made responsible for unloading and is familiar with the nature and properties of the material being unloaded;
2) The employee responsible for unloading is instructed in the procedures to be followed during unloading and in the event of an emergency, and has the authority and ability to halt the flow of product immediately and take emergency action;
3) In the event of an emergency, the system must be capable of immediately halting the flow of product or alerting the employee responsible for unloading; and
4) The monitoring device must provide immediate notification of any malfunction to the person responsible for unloading, or the device is checked hourly for malfunctions.
Amber Chemical should be aware that, in case of malfunction, the device (i.e., proposed non-human monitoring system) may no longer be relied upon and instead the individual responsible for unloading must constantly observe the unloading.
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.