At CO2Meter, we are often asked, "What CO2 level is dangerous?" CO2 levels above 40,000ppm (4%) are life threatening. However, there are many other limits placed on carbon dioxide levels depending on your application.
These limits are defined by agencies such as the Occupational Health and Safety Administration (OSHA) and other regulatory bodies as described in this article.
Even if you don't realize it, inspection codes are always being updated or added to. At CO2Meter, we want to help our partners and customers understand these codes and know what to do to ensure code compliance and protection. The ultimate goal is to keep people safe and that requires a constant cycle of understanding the continual code updates and their additions.
For most states in the US, a workplace safety standard is set that defines CO2 danger levels as 5,000ppm for an 8-hour period or 30,000ppm for a 15 minute period. This means the average concentration over a 15 minute period should not exceed 30,000ppm.
Note that carbon dioxide is not generally found at hazardous levels unless there is limited ventilation where gas is being stored or produced, or where the room is considered a confined or enclosed space.
Below we highlight the specific carbon dioxide compliance codes and standards so businesses are aware of and familiar with the requirements, CO2 sensor installation and testing protocols.
High pressure CO2 cylinders and low pressure bulk tanks used by restaurants and breweries for their soft-drink and draft beer systems or by commercial indoor growers are regulated by the National Board Inspection Code (NBIC).
The NBIC was originally called the National Board of Boiler and Pressure Vessel Inspectors. You are probably wondering why a boiler inspector would be interested in a CO2 cylinder or tank. It's because the CO2 tanks are pressure vessels.
The NBIC codes were first published in 1946 as a guide for chief boiler inspectors. Since that time, it has become the recognized standard for the installation, inspection, and repair and/or alteration of boilers, pressure vessels, and pressure relief devices.
The early codes for carbon dioxide from the NBIC discussed the need for specified alarm set points based on OSHA requirements and that a warning device must be located outside the hazard room to pre-warn occupants of dangerous CO2 levels.
The National Board Inspection Code (NBIC) was one of the first to codify requirements for CO2 monitoring in their 2012 edition.
Even in states that do not officially adopt the NBIC codes, it is often used as the de facto standard for local inspection and code enforcement.
The NBIC and its explanations fare revised every 2 years to insure that the regulations meet the changing nature of technology. The most recent change is the 2021 edition with revised carbon dioxide gas detection system requirements for Liquid Carbon Dioxide storage vessels (section S3.4 and S12.5).
NBIC codes are created by a rotating committee of boiler and pressure vessel engineers and experts. These experts update the code and provide guidance and information to those organizations that manufacture, install, repair, and own/use any pressure vessels. It also provides direction to government organizations and inspectors as to how to fairly apply the regulations for the installation and use of the equipment.
The NBIC speaks very directly to the storage of CO2 and monitoring - not just bulk tanks - but cylinders as well. This is explained in an excerpt below from Part 1, Supplement 3 of the 2018 NBIC relating to Installation of Liquid Carbon Dioxide Storage Vessels.
NBIC S3.4 Gas Detection Systems
Rooms or areas where carbon dioxide storage vessel(s) are located indoors or in enclosed or below grade outdoor locations shall be provided with a gas detection and alarm system for general area monitoring that is capable of detecting and notifying building occupants of a CO2 gas release. Alarms will be designed to activate a low level pre-alarm at 1.5% concentration of CO2 and a full high alarm at 3% concentration of CO2 (which is the OSHA & ACGIH 15 minute and NIOSH 10 minute Short Term Exposure Limit for CO2.) These systems are not designed for employee personal exposure monitoring. Gas detection systems shall be installed and tested in accordance with manufactures installation instructions and the following requirements;
- Activation of the gas detection system shall activate an audible alarm within the room or area in which the carbon dioxide storage vessel is located.
- Audible alarms shall also be placed at the entrance(s) to the room or area where the carbon dioxide storage vessel and/ or fill box is located to notify anyone who might try to enter the area of a potential problem.
NBIC S3.5 Signage
Warning signs shall be posted at the entrance to the building, room, enclosure, or enclosed area where the container is located. The warning sign shall be at least 8 in (200mm) wide and 6 in (150 mm) high. The wording shall be concise and easy to read and the upper portion of the sign must be orange as shown in figure S3.5. The size of the lettering must be as large as possible for the intended viewing distance and in accordance with jurisdictional requirements. When no jurisdictional requirements exist, the minimum letter height shall be in accordance with NEMA American National Standard for Environmental and Facility Safety Signs (ANSI Z535.2). The warning signs shall state the following:
- "WARNING – CARBON DIOXIDE GAS. Ventilate the area before entering. A high carbon dioxide (CO2) gas concentration in this area can cause suffocation.”
Additional instruction signage shall be posted outside of the area where the container is located and such signage shall contain at minimum the following information:
- Carbon Dioxide Monitors for general area monitoring (not employee personal exposure monitoring) are provided in this area. These monitors are set to alarm at 15,000ppm (1.5% concentration) for the low level alarm and at 30,000ppm (3% concentration) for high level alarm.
- Low Level Alarm (15,000ppm) – Provide appropriate cross ventilation to the area. Personnel may enter area for short periods of time (not to exceed 15 minutes at a time) in order to identify and repair potential leaks.
- High Level Alarm (30,000ppm) – Personnel should evacuate the area and nobody should enter the affected area without proper self contained breathing apparatus until the area is adequately ventilated and the concentration of CO2 is reduced below the high alarm limit.
(pdf., English and Spanish).
NBIC Code Updates
The NBIC code was recently updated July 2021, having been accepted by the committee and included the following revisions:
Revised carbon dioxide gas detection system requirements for Liquid Carbon Dioxide storage vessels.
New requirements for remote visual inspection for confined space entry.
Several revisions/updates to the inspection requirements for PVHOs (pressure vessel for human occupancy).
Revised carbon dioxide gas detection system requirements for Liquid Carbon Dioxide storage vessels.
The NBIC also includes Standard Welding Procedure Specifications (SWPS) and requirements for NO2 measurement which have been strengthened in several circumstances.
OSHA & NIOSH Guidelines
Unlike the NBIC, the Occupational Safety and Health Administration - OSHA and the National Institute of Occupational Safety and Health - NIOSH rules and laws cover more than just the CO2 storage vessels. OSHA is uniquely interested in the health and safety of all employees in commercial workspaces.
For CO2, OSHA and NIOSH have created laws and regulations for CO2 exposure for workers that state that no lower than 5,000 ppm TWA (time weighted average) should be utilized for the first alarm, 15,000 ppm as the half STEL (short term exposure limit), 30,000 ppm as the STEL, and 40,000 ppm as IDLH (immediately dangerous to life or health). These standards are fixed by OSHA and do not change.
The next organization to include regulations around stored CO2, CO2 safety, and safety monitoring is the National Fire Protection Association (NFPA). Since the early NFPA regulations did not have a nice, neat place to put CO2 monitoring requirements, they "squeezed" them into NFPA 55 Cryogenic Fluids codes.
Here is a humorous note - CO2 is NOT a cryogenic fluid!
The NFPA 1 & 55 are considered to be the most "vanilla” of all the codes as it relates to CO2 because it mandates almost no specifics about devices, locations, or performance. The last update to the NFPA 55 was released in 2020.
Both NFPA 1 & 55 reference the need for gas detection wherever an known gas is stored. Both sections provide some specifics that should be reviewed with your local jurisdictional authority.
Updates are in place to NFPA 1 in the 2023 edition but only for cannabis facilities. Other organizations are preparing requested updates to NFPA 55 to bring the code more into alignment with other codes.
The last organization that has mandated CO2 monitoring is the International Fire Code (IFC). The IFC is part of the International Code Council (ICC) that also creates building, electrical, plumbing and other codes. The IFC has traditionally been the code that is more prescriptive about devices, locations, and alarm setpoints. Some of the common recommendations in the IFC include:
- 12 inches from the floor-mounted height for sensors
- First alarm at 5,000 ppm instantaneous
- A safety monitor or increased ventilation is required whenever 100 lbs. or more of CO2 is stored.
Compressed Gas Association CO2 Resources
The Compressed Gas Association (CGA) is a trade association that represents the interests of the industrial, medical, and food gases industry. It is based in the United States and was founded in 1913. The CGA develops and publishes standards and guidelines related to the safe manufacture, transportation, storage, and use of compressed gases.
The CGA also highlights carbon dioxide (CO2) safety, best practices, and provides gas safety resources for anyone who is handling or using CO2 in the workplace. Because CO2 can pose additional hazards from overexposure or from dry ice handling, the CGA safety posters and resources can be used to support the safe use of the gas.
Below we highlight the CGA recommended resources for best practice and safety guideline in the field:
- CGA G-6, Carbon Dioxide
- CGA G-6.9, Dry Ice
- CGA G-6.1, Standard for Insulated Liquid Carbon Dioxide Systems at Consumer Sites
- CGA G-6.5, Standard for Small Stationary Insulated Carbon Dioxide Supply Systems
- CGA G-6.7, Safe Handling of Liquid Carbon Dioxide Containers that Have Lost Pressure
Free CGA Safety Materials
- CGA SP-15, Safety Poster (End User), Safe Handling, Transport, and Use of Dry Ice
- CGA SP-16, Safety Poster (End User), Safe Use of Refrigerated & Cryogenic Liquids
- CGA SP-9, Safety Poster (Industrial), Enclosed Spaces Can Be Unsafe
ASHRAE Standards for Acceptable Air Quality
In the United States, the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) sets guidelines for acceptable levels of CO2 in buildings. According to the Summary of Selected Air Quality Guidelines in ASHRAE Standard 62.1-2016, "Ventilation for Acceptable Indoor Air Quality"
“CO2 at very high concentrations (e.g. greater than 5,000 parts-per-million) can pose a health risk…However, in most buildings, concentrations almost never rise to these levels. CO2 at the concentrations commonly found in buildings is not a direct health risk, but CO2 concentrations can be used as an indicator of occupant odors (odorous bioeffluents) and occupant acceptance of these odors. At the activity levels found in typical office buildings, steady-state CO2 concentrations of about 700 ppm above outdoor air levels indicate an outdoor air ventilation rate of about 7.5 L/s/person (15 cfm/person). Laboratory and field studies have shown that this rate of ventilation will dilute odors from human bioeffluents to levels that will satisfy a substantial majority (about 80%) of unadapted persons (visitors) in a space…”
CO2 concentrations in outdoor air is about 400ppm. Therefore, ASHRAE recommends indoor CO2 levels to be no more than 1,100ppm. The Occupational Safety and Health Association (OSHA) standards state that 5,000ppm of CO2 is the maximum level allowed for workers over an 8-hour average, and this limit is a requirement in most building codes.
The Authority Having Jurisdiction
One of the keys to accurately and effectively monitoring to meet codes is to know specifically what your jurisdiction requires. This isn't always easy. AHJ's can require more prescriptive codes but not less.
CO2Meter recommends you contact your local fire inspector (aka the AHJ) and ask specifically what they require. Inspectors are always open to proactive individuals as it demonstrates your desire to meet their codes and keep your staff and the public safe.
CO2 Code Inspection Tips
Here are a few helpful resource notes for you to check if you are required to have a CO2 monitor.
- Start at the state level. Contact the offices of the State Fire Marshal, Building Inspector, and the Head of the Boiler and Pressure Vessel division. Why the Boiler Inspector? Your state's Boiler Inspector is in charge of enforcing the state and national regulations for boilers, and in most cases, pressure vessels. CO2 storage tanks ARE pressure/storage vessels and can be regulated by these codes. To search for your states Boiler Inspector visit http://www.nationalboard.org/ViewAllSynopses.aspx and search by your state.
- Move to the local level. In some states like Texas the state has abdicated responsibility for the adoption and enforcement of these regulations and codes to local officials. Check with the Fire Marshall and Building Inspector in your town and ask if they have or are considering a code for CO2 monitoring. Know whether your local officials are considering a change.
- The major issue with leaving code creation to local officials is that it creates a jumbled array of codes across the state. Municipalities next to each other could have completely different codes. For Example: If you are a small business owner you may be required to have a monitor in South Miami but not in North Miami. This “wild west show” leads to ambiguity and confusion for business owners trying to do the right thing for their employees and guests. And know that even though North Miami doesn’t have a code today, they will enact one as soon as they figure out that South Miami has one (and is making money off of it too).
- Inquire with your CO2 supplier about the codes. They can be helpful and may have a process and devices in place to help you meet the code.
- These regulations apply to anyone that is storing or creating CO2. Hospitals and medical facilities, breweries, restaurants and bars, indoor growers, welding shops, and industry should all be mindful that changing CO2 regulations may mean that what was not required yesterday may be required next week. Assign the responsibility of checking regularly to someone on your team.
CO2 Safety Monitors that Meet the Code
In response to CO2 safety monitoring and compliance, the Remote CO2 Storage Safety Alarm (RAD-0102-6) continues to meet the increased requirements for the OSHA STEL (Short Term Exposure Limit) with alarms at 1.5%, and at 3% CO2.
This device is designed to protect customers and workers near stored carbon dioxide and is also designed to meet NFPA, IFC, and NBIC Requirements. In addition, the monitor features both audible and visual alarms and 3 built-in relays that can control an exhaust fan or send an alarm to the fire department or monitoring company.
Dependent upon your jurisdiction and application, CO2Meter also provides additional monitoring devices and accessories to meet specific regulations prior to inspection.
Below are our devices that meet fire code compliance:
- CO2 Multi-Sensor System
- CO2 Storage Safety 3 Alarm
- CO2 Storage Safety 3 Alarm Strobe Lights
- CO2 Storage Safety Strobe Tower
- CO2 Solenoid Shut Off Valve
Where to place a CO2 Safety Monitor?
Deciding if your business or work area is suitable for a CO2 monitor can be concerning. As CO2 safety monitors are critical and must be installed, yet there are areas of limitation.
If you are nervous about calling an inspector proactively, or do not feel comfortable doing so, contact us about the requirements for your local jurisdiction. We are happy to help.