Combustible Dust Testing

Laboratory testing to quantify dust explosion and reactivity hazards

Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Gas and Vapor

Laboratory testing to quantify explosion hazards for vapor and gas mixtures

Classification of hazardous materials subject to shipping and storage regulations
Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen
Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Thermal Stability

Safe storage or processing requires an understanding of the possible hazards associated with sensitivity to variations in temperature

Adiabatic Calorimetry
Data demonstrate the consequences of process upsets, such as failed equipment or improper procedures, and guide mitigation strategies including Emergency Relief System (ERS) design
Reaction Calorimetry
Data yield heat and gas removal requirements to control the desired process chemistry
Battery Safety

Testing to support safe design of batteries and electrical power backup facilities particularly to satisfy UL9540a ed.4

Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Cable Testing
Evaluate electrical cables to demonstrate reliability and identify defects or degradation
Equipment Qualification (EQ)
Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions
Water Hammer
Analysis and testing to identify and prevent unwanted hydraulic pressure transients in process piping
Acoustic Vibration
Identify and eliminate potential sources of unwanted vibration in piping and structural systems
Gas & Air Intrusion
Analysis and testing to identify and prevent intrusion of gas or air in piping systems
ISO/IEC 17025:2017

Fauske & Associates fulfills the requirements of ISO/IEC 17025:2017 in the field of Testing

ISO 9001:2015
Fauske & Associates fulfills the requirements of ISO 9001:2015
Dust Hazards Analysis
Evaluate your process to identify combustible dust hazards and perform dust explosion testing
On-Site Risk Management
On-site safety studies can help identify explosibility and chemical reaction hazards so that appropriate testing, simulations, or calculations are identified to support safe scale up
DIERS Methodology
Design emergency pressure relief systems to mitigate the consequences of unwanted chemical reactivity and account for two-phase flow using the right tools and methods
Deflagrations (Dust/Vapor/Gas)

Properly size pressure relief vents to protect your processes from dust, vapor, and gas explosions

Effluent Handling

Pressure relief sizing is just the first step and it is critical to safely handle the effluent discharge from an overpressure event

FATE™ & Facility Modeling

FATE (Facility Flow, Aerosol, Thermal, and Explosion) is a flexible, fast-running code developed and maintained by Fauske and Associates under an ASME NQA-1 compliant QA program.

Mechanical, Piping, and Electrical
Engineering and testing to support safe plant operations and develop solutions to problems in heat transfer, fluid, flow, and electric power systems
Hydrogen Safety
Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen
Thermal Hydraulics
Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions
Nuclear Safety
Our Nuclear Services Group is recognized for comprehensive evaluations to help commercial nuclear power plants operate efficiently and stay compliant
Radioactive Waste
Safety analysis to underpin decomissioning process at facilities which have produced or used radioactive nuclear materials
Adiabatic Safety Calorimeters (ARSST and VSP2)

Low thermal inertial adiabatic calorimeters specially designed to provide directly scalable data that are critical to safe process design

Other Lab Equipment and Parts for the DSC/ARC/ARSST/VSP2 Calorimeters

Products and equipment for the process safety or process development laboratory


Software for emergency relief system design to ensure safe processing of reactive chemicals, including consideration of two-phase flow and runaway chemical reactions


Facility modeling software mechanistically tracks transport of heat, gasses, vapors, and aerosols for safety analysis of multi-room facilities


Our highly experienced team keeps you up-to-date on the latest process safety developments.

Process Safety Newsletter

Stay informed with our quarterly Process Safety Newsletters sharing topical articles and practical advice.


With over 40 years of industry expertise, we have a wealth of process safety knowledge to share.

Recent Posts

Hybrid Mixtures - Is Your Explosive Dust Testing Giving You Applicable Data?

Posted by Fauske & Associates on 10.01.20

It is necessary, and often mandated, that explosive dusts be characterized in order to help develop a mitigation plan for explosion hazards, which in turn ensures increased process safety. Typically, dust explosivity testing is performed under standardized, ambient conditions as outlined by ASTM and other international standards. However, numerous industrial processes do not occur under these standard conditions. For example, the process may occur in the presence of a fuel vapor, fuel gas, and/or at an elevated temperature, all of which could affect the dust explosivity properties and thus effect the requirements for mitigating the hazard.


Combustible dust clouds that form in the presence of a fuel vapor or gas are often referred to as hybrid mixtures. Hybrid mixtures are commonly present in situ when a process requires the use of a volatile solvent during chemical synthesis (e.g. alcohols, benzene derivatives), gases from decomposition products (carbon monoxide from smoldering material), or if a natural fuel gas is present in the environment (e.g. mining). Currently, it is not common practice to determine the explosivity characteristics of hybrid mixtures. Instead, the explosivity of the dust alone is tested, which can lead to much different results compared to the hybrid mixture. Although current testing of hybrid mixtures is limited, preliminary data suggests that the presence of fuel vapors in the presence of explosive dusts likely decreases the minimum explosible concentration (MEC), increases the max explosion overpressure (Pmax), increases the max normalized rate of pressure rise of explosion (Kmax), and decreases the limiting oxygen concentration (LOC) for an explosion.[1–3] all of which would affect the hazard assessment. Thus, explosivity testing should be performed on hybrid mixtures, and not on explosive dusts alone, to ensure the test results better reflect the hazards associated with the specific process. This will ultimately lead to improved hazard mitigation and enhanced process safety. Fauske & Associates, LLC (FAI) has the capabilities to perform hybrid mixture testing using modified ASTM and EN standards that parallel industrial processes.


To demonstrate our capabilities, we have chosen to perform explosivity testing on a hybrid mixture containing Creatine HCl, a common dietary supplement, and ethanol. This hybrid mixture is likely to form in situ during the last step in Creatine HCl synthesis when the product is washed with ethanol to remove impurities. We have determined the MEC, explosion severity data, and LOC for pure ethanol vapor, pure Creatine HCl, and then a hybrid mixture containing an ethanol atmosphere and Creatine HCl. We then use this data to assess the differences in hazards between pure Creatine HCl and the hybrid mixture.

hybrid mixtures testing apparatus

Figure 1. Testing apparatus including: 20 L Siwek chamber with jacket, temperature controllable water recirculator for the jacket, custom front panel, and dispersion gas storage tank with controllable heating wrap.

Testing was performed using a standard 20-L Siwek chamber with slight modifications (Figure 1). A fuel introduction port, a gas addition/sampling port, and a thermocouple port was fixed to the front of the chamber. The internal chamber temperature was controlled using a temperature controlled water recirculator for the 20-L vessel’s jacket and by wrapping a dispersion gas storage vessel with a controllable heating wrap. Internal chamber temperature was monitored using a calibrated thermocouple. A partial ethanol vapor atmosphere was generated in the chamber by evacuating the chamber to a pressure below 100 mbara, fixing a syringe containing a desired amount of ethanol to the air-tight front fuel port, injecting the ethanol, and observing the coinciding desired pressure rise. Testing was conducted in accordance to modified ASTM standards.


Reagent grade, pure ethanol purchased from Sigma-Aldrich was and pure Creatine HCl purchased from pure Creatine HCl purchased from was used for testing. The Creatine HCl was found to have a percent weight moisture content of 0.26%, a mean particle diameter of 193 µm, with 31.11% of the particles were less than 75 µm.


The MEC, Pmax, Kmax, average peak explosivity concentration, and LOC for pure ethanol were determined at 36°C ± 3°C (Table 1). 36°C was chosen because large volumes of ethanol were rapidly vaporized at this temperature under the pressure conditions during introduction. All measured explosivity values for ethanol are in general agreement with literature values [1–3], although the literature values were determined under ambient temperature conditions.

Explosivity data for pure ethanol vapor

Given the MEC of the pure ethanol under the elevated temperature conditions, a 1% ethanol atmosphere was chosen for hybrid mixture testing to ensure that any explosivity exhibited by the mixture could be attributed to the vapor-dust hybrid mixture and not ethanol vapor alone. Testing of Creatine HCl and the hybrid mixture was performed at 32°C ± 3°C because the desired amount of ethanol was rapidly volatilized under these conditions. Additionally, a 1% ethanol atmosphere at 32°C also reflects a plausible process condition.


The MEC, Pmax, Kmax, average peak explosivity concentration, and LOC for Creatine HCl and hybrid mixture of Creatine HCl and 1% ethanol atmosphere were determined at 32°C ± 3°C (Table 2). In comparison to pure Creatine HCl, the hybrid mixture was determined to have a lower MEC, higher Pmax, higher Kmax, lower average peak explosivity concentration, and lower LOC. These general trends agree with previously published data for hybrid mixtures of various dusts and alcohol vapors [1–3].


The addition of a 1% ethanol vapor atmosphere decreased the MEC of Creatine HCl from 750 to 40 g/m3. This result suggests that extra care should be taken to ensure small Creatine HCl dust clouds do not form as even small dust clouds have explosive properties in the presence of ethanol vapor. While the Pmax and Kmax values for the hybrid mixture are slightly higher than values for pure Creatine HCl, both the pure sample and hybrid mixture would be classified as St1 explosions. While St1 explosions typically require similar risk management systems, the hybrid mixture exhibits peak explosivity characteristics at a concentration ~5 times lower than the pure compound. Again, this serves as further evidence that extra precautions should be taken to ensure that even small concentration Creatine HCl dust clouds do not form in the presence of an ethanol atmosphere. The LOC of the hybrid mixture was determined to be 5% lower than the LOC of Creatine HCl alone. Meaning, in the presence of an ethanol atmosphere, additional inerting gas would be needed to mitigate any possible explosivity hazards. In total, the differences in test results suggest the hybrid mixture is likely to present an increased and more complex explosion hazard risk compared to the pure dust alone.


Our hybrid mixture testing results further substantiate the idea that explosion testing should be performed on hybrid mixtures, and not dust alone, when specific processes may lead to hybrid mixture formation. It is extremely important to perform testing on hybrid mixtures when relevant, because the presence of a fuel vapor or gas can lead to much more dangerous explosivity characteristics, thus it will affect the hazard mitigation strategies needed to maintain process safety. Luckily, we at FAI have the tools, knowledge, and experience needed to perform modified explosion testing methods on hybrid mixtures under conditions that match your process. Contact us today!

Contact Us


  1. E.K. Addai, M. Clouthier, P. Amyotte, M. Safdar, U. Krause, Experimental investigation of limiting oxygen concentration of hybrid mixtures, Journal of Loss Prevention in the Process Industries. 57 (2019) 120–130.
  2. E.K. Addai, A. Aljaroudi, Z. Abbas, P. Amyotte, A. Addo, U. Krause, Investigation of the explosion severity of multiphase hybrid mixtures, Process Safety Progress. n/a (n.d.) e12139.
  3. E.K. Addai, H. Ali, P. Amyotte, U. Krause, Experimental and theoretical investigation of the lower explosion limit of multiphase hybrid mixtures, Process Safety Progress. 38 (2019) e12045.

Topics: Combustible Dust


Is My Dust Combustible?

A Flowchart To Help You Decide
Download Now