Ensuring the safety of employees who are regularly exposed to harmful chemicals is never easy. That’s where the concept of STEL (Short-Term Exposure Limit) becomes important. It defines the maximum short-term duration a worker can safely be exposed to a specific chemical. 

In your organization, you may already have quick access to SDSs and well-updated emergency preparedness measures. But if you don’t know how to measure this small yet critical parameter, your workplace could still be at risk. 

This guide will help you learn what STEL really means and how your organization can effectively measure it. 

What is STEL? 

STEL, or Short-Term Exposure Limit, is the maximum amount of a chemical that a worker can safely be exposed to for a short period. It’s usually for 15 minutes. Mainly, it’s designed to protect employees from the harmful effects of sudden or brief exposure to dangerous substances.  

Some Key Points to Know about STEL 

  • STEL is Based on a 15-Minute Exposure Period

This means the measurement of chemical exposure is taken over 15 minutes. If the chemical level stays within the safe limit during this time, it is considered acceptable. 

 

  • Workers should not be Exposed More than 4 Times a Day at this Level   

Even if short-term exposure is within the limit, repeating it too many times can still be harmful. That’s why exposure to STEL is restricted to a maximum of four times in one workday. 

 

  • There must be at Least 60 minutes between each Exposure

After being exposed to chemicals at the STEL limit, the body needs recovery time. A one-hour gap ensures workers are not continuously exposed without a break. 

 

  • It’s all about Short-Term Safety, not the Full-Day Average

Unlike long-term exposure limits (like TWA, which averages over 8 hours), STEL only looks at short bursts. This protects workers from sudden health effects like irritation, dizziness, or breathing issues that can happen in just a few minutes. 

 

Why is Measuring STEL Important? 

Measuring STEL is crucial because: 

  • Some Chemicals can be Harmful in just a few Minutes

Substances like chlorine, ammonia, or formaldehyde can cause irritation to the eyes, nose, throat, or even breathing problems almost immediately. By measuring STEL, you can identify these short-term spikes in exposure before they become dangerous. 

  • It Keeps your Workplace Compliant with Safety Regulations 

Agencies like OSHA and ACGIH have set limits for chemical exposure. Regularly checking STEL ensures that your organization is following these rules and avoiding penalties or legal issues. 

  • It Protects Employee Health and Productivity

Even brief exposure to high levels of chemicals can make workers feel dizzy, tired, or unfocused. Over time, this can harm their health and lower their performance at work. Measuring STEL helps create a safer and more supportive environment where employees can do their jobs without unnecessary risks. 

Step-by-Step Guide to Measuring STEL 

Now let’s get practical. How do you actually measure STEL in your workplace? 

Step 1: Identify Hazardous Chemicals 

Start with your chemical inventory. Which chemicals in your workplace have a defined STEL value? You can usually find this in the Safety Data Sheet (SDS) under the exposure limits section. Example: Chlorine has an OSHA STEL of 1 ppm (parts per million). 

 

Step 2: Choose the Right Monitoring Device 

You’ll need air sampling equipment or direct-reading instruments such as 

  • Gas detectors (portable or fixed) 
  • Personal sampling pumps with chemical-specific filters or tubes 

Make sure your device can record concentrations over a short period (like 15 minutes). 

 

Step 3: Set Up the Monitoring Period 

Since STEL is based on 15 minutes, you should measure chemical levels continuously during this time frame. 

  • Place the sampling device close to the worker’s breathing zone (usually near the collar or shoulder). 
  • Start recording when exposure begins. For example, when a worker mixes or transfers a chemical. 

 

Step 4: Collect and Record Data 

  • If you’re using a direct-reading monitor, it will display concentration levels in real time. 
  • In case you’re using a sampling pump, you’ll need to analyze the collected sample later in a lab. 

So, keep accurate records of: 

  • The chemical name 
  • Sampling start and end time 
  • Concentration levels recorded 

Step 5: Compare with STEL Limits 

Once you have the data, compare the results with the STEL value provided by OSHA, ACGIH, or your local regulatory authority. 

 For example: If chlorine’s STEL is 1 ppm and your monitoring shows 1.5 ppm, that’s a violation. 

 

Step 6: Take Corrective Actions 

If the results are above the STEL: 

  • Improve ventilation (install exhaust systems, fume hoods, etc.). 
  • Provide workers with the right PPE (like respirators). 
  • Limit the duration of exposure by rotating tasks. 
  • Update your safety training so employees know the risks. 

How Can an SDS Management Software Help? 

  • Quick Access to Exposure Limits

An SDS management software gives you instant access to important details like STEL, TWA, and Ceiling limits for every chemical. Due to this, you don’t have to manually search through paper files or spreadsheets. 

 

  • Always Up-to-Date Information 

It ensures your SDSs are regularly updated. As a result, your team always works with the most accurate and compliant data. 

 

  • Centralized Storage and Sharing

All SDSs are stored in one system. This makes it easy to organize, share, and retrieve information whenever needed—whether during daily operations or emergencies. 

 

  • Improved Training and Awareness 

Employees can quickly learn about chemical risks and safe handling practices by accessing the software. It helps them stay informed and safe on the job. 

 

  • Stronger Compliance and Safety

By keeping exposure data and safety measures in one place, the software makes it easier to follow OSHA and other regulatory requirements. This way, it reduces the risk of violations or accidents. 

Conclusion 

Measuring STEL may sound technical. However, it’s really about keeping your people safe during short-term exposures. With the right equipment, proper monitoring, and regular checks, you can make sure your workplace stays within safe limits. 

Remember, it only takes a few minutes of high exposure to cause harm. By measuring and controlling STEL, you’re not just ticking a compliance box. Thus, you’re protecting your team’s health and building a safer workplace.