--- title: "Cal/OSHA PEL Limits: CO, CO₂, H₂S, SO₂ | Aethair" description: "Cal/OSHA Permissible Exposure Limits (8 CCR §5155, Table AC-1) limit values for Carbon Monoxide, Carbon Dioxide, Hydrogen Sulfide, Sulfur Dioxide, and…" url: https://aethair.io/standards/cal_osha_pel/ --- Compliance · Cal/OSHA # Cal/OSHA Permissible Exposure Limits (8 CCR §5155, Table AC-1) Occupational: legal limit (California), 8-hour TWA unless noted California sets its own workplace exposure limits in **8 CCR §5155, Airborne Contaminants**, whose **Table AC-1** lists a permissible exposure limit (8-hour TWA), a short-term exposure limit (15-minute), and a ceiling for each regulated substance. Cal/OSHA has updated its table far more recently than federal OSHA, so many values are stricter. Examples include **carbon monoxide at 25 ppm with a 200 ppm ceiling** (federal: 50 ppm); **ozone at 0.1 ppm with a 0.3 ppm STEL**; **sulfur dioxide at 2 ppm with a 5 ppm STEL**; **hydrogen sulfide at 10 ppm with a 15 ppm STEL and a 50 ppm ceiling**; and **nitrogen dioxide with a 1 ppm STEL**. [Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Configure Cal/OSHA PEL Monitoring](https://aethair.io/build/?params=co,co2,h2s,so2,no,no2,o3,nh3,cl2,hg,hcl,hf,btex) At a glance **Cal/OSHA** Occupational: legal limit (California), 8-hour TWA unless noted 13 parameters · 25 limit values [Carbon Monoxide (CO)](https://aethair.io/parameters/co/) [Carbon Dioxide (CO₂)](https://aethair.io/parameters/co2/) [Hydrogen Sulfide (H₂S)](https://aethair.io/parameters/h2s/) [Sulfur Dioxide (SO₂)](https://aethair.io/parameters/so2/) [Nitric Oxide (NO)](https://aethair.io/parameters/no/) [Nitrogen Dioxide (NO₂)](https://aethair.io/parameters/no2/) [Ozone (O₃)](https://aethair.io/parameters/o3/) [Ammonia (NH₃)](https://aethair.io/parameters/nh3/) [Chlorine (Cl₂)](https://aethair.io/parameters/cl2/) [Mercury (Hg)](https://aethair.io/parameters/hg/) [Hydrogen Chloride (HCl)](https://aethair.io/parameters/hcl/) [Hydrogen Fluoride (HF)](https://aethair.io/parameters/hf/) [BTEX / speciated VOC](https://aethair.io/parameters/btex/) 2 devices measure them all - **Aethair PRO** Aethair O₃+NO₂ · Aethair CO (electrochemical) · Custom MultiSense - **Thiamis** RAE Gas Detectors · Defiant Technologies Specialty Air Analyzers · AMETEK Brookfield Specialty Air Analyzers [Official text from Cal/OSHA](https://www.dir.ca.gov/title8/5155.html) Limit values ## Cal/OSHA PEL Limit Values Every value Cal/OSHA publishes for the 13 parameters below, with its averaging period, as the standard states it. [**Carbon Monoxide (CO)** Gases & VOCs](https://aethair.io/parameters/co/) **25 ppm** *8-hour TWA (PEL)* **200 ppm** *Ceiling* [**Carbon Dioxide (CO₂)** Gases & VOCs](https://aethair.io/parameters/co2/) **5000 ppm** *8-hour TWA (PEL)* **30000 ppm** *STEL* [**Hydrogen Sulfide (H₂S)** Gases & VOCs](https://aethair.io/parameters/h2s/) **10 ppm** *8-hour TWA (PEL)* **15 ppm** *STEL* **50 ppm** *Ceiling* [**Sulfur Dioxide (SO₂)** Gases & VOCs](https://aethair.io/parameters/so2/) **2 ppm** *8-hour TWA (PEL)* **5 ppm** *STEL* [**Nitric Oxide (NO)** Gases & VOCs](https://aethair.io/parameters/no/) **25 ppm** *8-hour TWA (PEL)* [**Nitrogen Dioxide (NO₂)** Gases & VOCs](https://aethair.io/parameters/no2/) **1 ppm** *STEL* [**Ozone (O₃)** Gases & VOCs](https://aethair.io/parameters/o3/) **0.1 ppm** *8-hour TWA (PEL)* **0.3 ppm** *STEL* [**Ammonia (NH₃)** Gases & VOCs](https://aethair.io/parameters/nh3/) **25 ppm** *8-hour TWA (PEL)* **35 ppm** *STEL* [**Chlorine (Cl₂)** Gases & VOCs](https://aethair.io/parameters/cl2/) **0.5 ppm** *8-hour TWA (PEL)* **1 ppm** *STEL* [**Mercury (Hg)** Gases & VOCs](https://aethair.io/parameters/hg/) **0.025 mg/m³** *8-hour TWA (PEL)* metallic and inorganic mercury **0.1 mg/m³** *Ceiling* metallic and inorganic mercury [**Hydrogen Chloride (HCl)** Gases & VOCs](https://aethair.io/parameters/hcl/) **0.3 ppm** *8-hour TWA (PEL)* **2 ppm** *Ceiling* [**Hydrogen Fluoride (HF)** Gases & VOCs](https://aethair.io/parameters/hf/) **0.4 ppm** *8-hour TWA (PEL)* as F **1 ppm** *STEL* as F [**BTEX / speciated VOC** Gases & VOCs](https://aethair.io/parameters/btex/) **1 ppm** *8-hour TWA (PEL)* benzene (see also section 5218) **5 ppm** *STEL* benzene Who it applies to ## Who Must Comply Employers in California. Where Cal/OSHA's limit is stricter than the federal PEL, the California value applies; OSHA's annotated PEL tables reproduce the Cal/OSHA values alongside the federal ones for comparison. Monitoring ## How Monitoring Demonstrates Compliance Each limit is compared with exposure over its own period: the 8-hour TWA for the PEL, 15 minutes for the STEL, any moment for a ceiling. Continuous monitoring is what shows a STEL or ceiling being approached, which a shift-average sample cannot; personal sampling in the breathing zone documents individual exposure. [Customize this configuration](https://aethair.io/build/?params=co,co2,h2s,so2,no,no2,o3,nh3,cl2,hg,hcl,hf,btex) ### Who measures each parameter | Parameter | Aethair PRO | Aethair IAQ | External | | - | - | - | - | | [Carbon Monoxide (CO)](https://aethair.io/parameters/co/) | CO (electrochemical), MultiGas+ +1 cartridges | — | [3 instruments](https://aethair.io/parameters/co/) via Thiamis | | [Carbon Dioxide (CO₂)](https://aethair.io/parameters/co2/) | CO₂ (dual NDIR), CO₂ (self-calibrating NDIR) cartridges | Built in | [2 instruments](https://aethair.io/parameters/co2/) via Thiamis | | [Hydrogen Sulfide (H₂S)](https://aethair.io/parameters/h2s/) | H₂S cartridge | — | [4 instruments](https://aethair.io/parameters/h2s/) via Thiamis | | [Sulfur Dioxide (SO₂)](https://aethair.io/parameters/so2/) | MultiSense, SO₂ cartridges | — | [1 instrument](https://aethair.io/parameters/so2/) via Thiamis | | [Nitric Oxide (NO)](https://aethair.io/parameters/no/) | NO cartridge | — | [1 instrument](https://aethair.io/parameters/no/) via Thiamis | | [Nitrogen Dioxide (NO₂)](https://aethair.io/parameters/no2/) | NO₂, MultiSense +1 cartridges | — | [1 instrument](https://aethair.io/parameters/no2/) via Thiamis | | [Ozone (O₃)](https://aethair.io/parameters/o3/) | O₃+NO₂ cartridge | — | [1 instrument](https://aethair.io/parameters/o3/) via Thiamis | | [Ammonia (NH₃)](https://aethair.io/parameters/nh3/) | — | — | [1 instrument](https://aethair.io/parameters/nh3/) via Thiamis | | [Chlorine (Cl₂)](https://aethair.io/parameters/cl2/) | — | — | [1 instrument](https://aethair.io/parameters/cl2/) via Thiamis | | [Mercury (Hg)](https://aethair.io/parameters/hg/) | — | — | [1 instrument](https://aethair.io/parameters/hg/) via Thiamis | | [Hydrogen Chloride (HCl)](https://aethair.io/parameters/hcl/) | HCl cartridge | — | — | | [Hydrogen Fluoride (HF)](https://aethair.io/parameters/hf/) | HF cartridge | — | — | | [BTEX / speciated VOC](https://aethair.io/parameters/btex/) | — | — | [1 instrument](https://aethair.io/parameters/btex/) via Thiamis | Devices ## Devices That Cover Cal/OSHA PEL How much of this standard one Aethair monitor covers, followed by the third-party instruments in the sensor catalog that measure its parameters. Each connects to Environet through a Thiamis gateway, which adds whatever the monitor leaves out. Aethair monitors [**Aethair PRO** Built in + Aethair O₃+NO₂, Aethair CO (electrochemical), Custom MultiSense (CO₂, H₂S, SO₂) 6 of 13: CO, CO₂, H₂S, SO₂, NO₂, O₃](https://aethair.io/products/pro/) Covers part of it (combine on one Thiamis) [**RAE** Gas Detectors 8 of 13: Cl₂, CO, CO₂, H₂S, NH₃, NO, NO₂, SO₂](https://aethair.io/sensors/rae-gas-detectors/) [**TSI GM460** Gas Detectors 2 of 13: CO, H₂S](https://aethair.io/sensors/tsi-gas-detectors/) [**RKI Instruments GX6000** Gas Detectors 2 of 13: CO, H₂S](https://aethair.io/sensors/rki-instruments-gas-detectors/) [**AMETEK Brookfield Jerome** Specialty Air Analyzers 2 of 13: H₂S, Mercury](https://aethair.io/sensors/ametek-brookfield-specialty-air-analyzers/) [**Defiant Technologies FROG** Specialty Air Analyzers 1 of 13: BTEX / speciated VOC](https://aethair.io/sensors/defiant-technologies-specialty-air-analyzers/) [**Particles Plus** Particulate & Dust Monitors 1 of 13: CO₂](https://aethair.io/sensors/particles-plus-particulate-dust-monitors/) [**2B Technologies POM** Specialty Air Analyzers 1 of 13: O₃](https://aethair.io/sensors/2b-technologies-specialty-air-analyzers/) Solutions ## Solutions Judged Against Cal/OSHA PEL ### [Occupational Safety & Industrial Hygiene](https://aethair.io/solutions/occupational-safety/) Worker exposure, confined space, and heat stress [All solutions](https://aethair.io/solutions/) Article Library ## Articles on Cal/OSHA PEL ### [Ozone Exposure Limits and Monitoring: OSHA and NAAQS](https://aethair.io/resources/ozone-monitoring-exposure-limits/) OSHA's ozone PEL is 0.1 ppm as an 8-hour TWA. How NIOSH, ACGIH, and the 70 ppb NAAQS compare, and why ozone needs short-interval monitoring. [All articles](https://aethair.io/resources/) Questions ## Cal/OSHA PEL FAQ What is the Cal/OSHA PEL for carbon monoxide? 25 ppm as an 8-hour time-weighted average, with a ceiling of 200 ppm, stricter than the federal [OSHA PEL](https://aethair.io/resources/osha-air-quality-standards-compliance/) of 50 ppm. What does Cal/OSHA set for ozone? A permissible exposure limit of 0.1 ppm as an 8-hour TWA and a short-term exposure limit of 0.3 ppm. Which limit applies in California, federal or Cal/OSHA? California employers follow Cal/OSHA's Table AC-1, which is stricter than the federal limits for many substances.