| The Home page of ILPI's Safety Data Sheet (SDS) Resource, the leader in SDS information since 1995! | |
| The history and philosophy behind this resource. | |
| A curated collection of books and reference materials concerning Safety Data Sheets and closely related topics. | |
| Paste your plain text SDS into the SDS-Demystifier, and it will be converted into a hypertext-enriched document with links to detailed explanations of each key term. | |
| An extensive list of frequently asked questions about Safety Data Sheets including regulations, content, compliance, and more. | |
| A humorous take on Safety Data Sheet jargon. Fill in the blanks on our entry form to generate a personalized Unsafety Data Sheet to share with your coworkers. | |
| Since 1995, we've maintained this massive curated list of the best places to find Safety Data Sheets on the Internet. | |
| Way more than a glossary, this hypertext-enhanced resource covers hundreds of SDS-related terms and expert knowledge. Each entry includes both the SDS relevance and links to additional authoritative resources. | |
| Archived results of Safety Data Sheet related polls taken by some of our millions of site visitors | |
| You are here! The OSHA regulations behind SDS regulations, including the inspection guidelines and over 400 official interpretations letters under the Hazard Communication Standard | |
| Commercial suppliers of SDS authoring and management software as well as cloud compliance services. | |
| Commercial companies that will create SDS's for your specific needs as well as SDS translation companies. |
Safety signs, banners, and scoreboards? Get yours at Safety Emporium!
OSHA Hazard Communication Letters of Interpretation
Ventilation for an anhydrous ammonia refrigeration system.
- Issued
- Record type
- Interpretation
- Historical standard
- 1910.1200, 1987 expanded rule (PDF)
- Current standard
- HCS 2024, as amended
ILPI assessment: HazCom training remains necessary; do not use historic alarm settings as current guidance
This letter addresses the obsolete 1987 version of the Hazard Communication Standard (HCS). Its HazCom conclusion remains consistent: workers need effective information and training about ammonia hazards. The separate engineering and emergency-response conclusions are site-specific and historical. In particular, the stated 2,500 ppm alarm and 40,000 ppm blower settings must not be used as general current protective design guidance.
NIOSH's current ammonia Pocket Guide lists 300 ppm as immediately dangerous to life or health (IDLH), far below those historical settings. The IDLH value is not itself an alarm-design setpoint. Current system design, ventilation and electrical classification require the applicable current codes and a competent site-specific evaluation; this review does not supply replacement setpoints.
Apply current information and training requirements, emergency-response requirements, and IDLH respiratory-protection procedures as applicable. Consult OSHA's ammonia-refrigeration resource for additional requirements, including process-safety management where covered. The 1989 ANSI/ASHRAE passages are not the current edition or an automatic clearance for present equipment.
Last reviewed: .
About this ILPI assessment
This comparison with current requirements is not a finding that OSHA has formally withdrawn this letter. This assessment reflects editorial judgment informed by human review and AI assistance. It is an opinion, may contain errors or omissions, and is not an official OSHA determination. For guidance on how OSHA requirements apply to your circumstances, contact your local OSHA office.
OSHA's notice about interpretation letters
The following notice is published on OSHA's interpretation pages; it is general guidance, not a letter-specific withdrawal notice.
OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.
Source: OSHA's original letter page.
June 13, 1990
MEMORANDUM FOR: LINDA R. ANKU
REGIONAL ADMINISTRATOR
FROM: PATRICIA K. CLARK
DIRECTOR DESIGNATE
DIRECTORATE Of COMPLIANCE PROGRAMS
SUBJECT: Dilution Ventilation and Intrinsic Safety
in the Mechanical Control Room for an
Anhydrous Ammonia Refrigeration System
Commercial kitchen safety begins with kitchen safety compliance products from Safety Emporium.
This is in response to your memorandum of April 9, regarding the above subject. As you know, the applicable industry consensus standards for refrigeration systems, including the system that uses ammonia as a refrigerant, are contained in ANSI/ASHRAE 15-1989. Section 10.14(j) of the ANSI/ASHRAE standard, however, precludes the ammonia refrigeration system control room from being classified as a Class I, Division 2 location, if the provisions contained in Sections 10.14(h) and 10.14(i) of the same standard are met.
The company at time of the inspection had not installed a ventilation system meeting the specifications of the ANSI/ASHRAE standard and, consequently, was in apparent violation of 1910.307(b), for exposing employees to explosion hazards. We advise that a 1910.307(b) citation be issued.
Because the company, [company name withheld], is proposing to install a ventilating system to meet the design requirements specified in the ANSI/ASHRAE standard, the company, will have abated 1910.307(b) violation when the system is installed. They would then not be required to install blower fans that are intrinsically safe.
It should be noted that the installation of a vapor detector system as described in your memorandum may potentially eliminate the explosion hazard but would not eliminate the inhalation hazards likely to cause death or serious physical harm.
The health hazards associated with ammonia are recognized by ANSI, as referenced in Table 2 of ANSI K61.1 - 1989 (copy attached), and a release of ammonia to contaminate the control room area in concentrations greater than 2,500 ppm in air, could be fatal if the necessary precautions are not taken. Though the referenced ANSI standard is not applicable to the situation you described, the inhalation hazard is recognized and must also be addressed by the company.
In order to protect against both safety and health hazards, the vapor detector system to be installed shall be capable of providing an audible alarm at an ammonia vapor concentration of 2,500 ppm in the air in the control room, and shall be capable of activating the exhaust blowers when the ammonia vapor concentration in the air in the control room reaches 40,000 ppm. Employees who may have to enter the control room during emergencies shall be fully equipped with the appropriate personal protective equipment, and shall be trained to meet OSHA standards at 1910.120 [ILPI: Original HAZWOPER 1989 (PDF) · Current HAZWOPER], 1910.134, and 1910.1200 [ILPI: Original HCS 1987 context (PDF) · Current HCS].
[ILPI note: At issuance: 1910.1200, 1987 expanded rule (PDF). Do not use these historical settings as current protective design guidance. NIOSH lists ammonia IDLH as 300 ppm; IDLH is not an alarm setpoint. Use current applicable engineering requirements and a site-specific evaluation, plus IDLH respiratory procedures.]
If your staff members have any questions, they may contact Sanji Kanth at FTS 523-8031.
The original official public domain version of this document is available from OSHA at https://www.osha.gov/laws-regs/standardinterpretations/1990-06-13-0.