Methyl mercaptan structureThe Occupational Safety & Health Administration (OSHA) has cited DuPont for 11 worker safety violations for a November, 2014, methyl mercaptan leak that killed four workers. The citations come with a total fine of $99,000.

Methyl mercaptan is used to make the insecticide methomyl. DuPont determined that more than 23,000 lb of methyl mercaptan was released in the incident, C&EN reports.

"The fatal incident occurred as one worker was overwhelmed when methyl mercaptan gas was unexpectedly released when she opened a drain on a methyl mercaptan vent line," an OSHA press release says. "Two co-workers who came to her aid were also overcome. None of the three wore protective respirators. A fourth co-worker - the brother of one of the fallen men - attempted a rescue, but was unsuccessful. All four people died in the building."

The OSHA citations involved violations of 29 CFR 1910 part 119, process safety management of highly hazardous chemicals; part 134, respiratory protection; part 165, employee alarm systems; and part 1000, air contaminants.

The specific citations are:

1.1 - Serious - 29 CFR 1910.119(d)(3)(i)(B): Process safety information pertaining to the equipment in the process did not include the piping and instrument diagrams (P&IDs).

1.2a - Serious - 29 CFR 1910.119(e)(1): The process hazard analysis was not appropriate to the complexity of the process and did not identify, evaluate, and control the hazards involved in the process.

1.2b - Serious - 29 CFR 1910.119(e)(3)(iii): The process hazards analysis did not address engineering and administrative controls applicable to the hazards and their interrelationships such as appropriate application of detection methodologies to provide early warning of releases.

1.3 - Serious - 29 CFR 1910.119(f)(1)(ii)(B): The employers written operating procedures covering operating limits did not address the steps required to correct deviations -In the Alternative- 29 CFR 191 0.119(J)(2): The employer did not establish and implement written procedures to maintain the on-going integrity of process equipment as required.

1.4 - Serious - 29 CFR 1910.119(f)(4): The employer did not develop and implement safe work practices to provide for the control of hazards during operations such as lockout/tagout; confined space entry; opening process equipment or piping; and control over entrance into a facility by maintenance, contractor, laboratory, or other support personnel. These safe work practices shall apply to employees and contractor employees.

1.5 - Serious - 29 CFR 1910.119(j)(5): Equipment deficiencies. The employer did not correct deficiencies in equipment that are outside acceptable limits (defined by the process safety information in paragraph (d) of this section) before further use or in a safe and timely manner when necessary means are taken to assure safe operation.

1.6a - Serious - 29 CFR 1910.119(l)(1): The employer did not establish and implement written procedures to manage changes to process chemicals, technology, equipment, and procedures; and, changes to facilities that affect a covered process.

1.6b - Serious - 29 CFR 1910.119(1)(4): Process safety information required by paragraph (d) of this section was not updated when a change covered by this paragraph resulted in a change in the process safety information.

1.7 - Serious - 29 CFR 1910.134(c)(1)(vii): The employer failed to train employees in the respiratory hazards to which they are potentially exposed during routine situations

1.8 - Serious - 29 CFR 1910.165(b)(1): The employee alarm system did not provide warning for reaction time for safe escape of employees from the workplace or the immediate work area, or both.

1.9a - Serious - 29 CFR 1910.1000(a)(1): Employee(s) were exposed to an airborne concentration of Methyl Mercaptan listed in Table Z-1 in excess of the ceiling concentration of 10 ppm.

1.9b - Serious - 29 CFR 1910.1000(e): Administrative or engineering controls were not used and implemented to achieve compliance with the limits prescribed in 29 CFR 1910.1000(a) through (d). When such controls were not feasible/available to achieve full compliance, protective equipment or any other protective measures were not used to keep the exposure of employees to air contaminants within the limits prescribed.

2.1 - Repeat - 29 CFR 1910.119(g)(1 )(i): Each employee presently involved in operating a process, and each employee before being involved in operating a newly assigned process, was not trained in an overview of the process and in the operating procedures as specified in paragraph (f) of this section. The training shall include emphasis on the specific safety and health hazards, emergency operations including shutdown, and safe work practices applicable to the employee's job tasks.

3.1 - Other-than-serious - 29 CFR 1910.119(h)(2)(vi): The employer shall maintain a contract employee injury and illness log related to the contractor's work in process areas.