Combustible Dust Testing

Laboratory testing to quantify dust explosion & reactivity hazards

Flammable Gas & Vapor Testing

Laboratory testing to quantify explosion hazards for vapor and gas mixtures

Chemical Reactivity Testing

Laboratory testing to quantify reactive chemical hazards, including the possibility of material incompatibility, instability, and runaway chemical reactions

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 safety handle the effluent discharge from an overpressure event

Thermal Stability

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


Classification of hazardous materials subject to shipping and storage regulations

Safety Data Sheets

Develop critical safety data for inclusion in SDS documents


Model transport of airborne virus aerosols to guide safe operations and ventilation upgrades


Model transport of contamination for source term and leak path factor analysis

Fire Analysis

Model transport of heat and smoke for fire analysis

Flammable or Toxic Gas

transport of flammable or toxic gas during a process upset

OSS consulting, adiabatic & reaction calorimetry and consulting

Onsite safety studies can help identify explosibility and chemical reaction hazards so that appropriate testing, simulations, or calculations are identified to support safe scale up

Mechanical, Piping, and Electrical

Engineering and testing to support safe plant operations and develop solutions to problems in heat transfer, fluid flow, electric power systems

Battery Safety

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

Hydrogen Safety

Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen

Spent Fuel

Safety analysis for packaging, transport, and storage of spent nuclear fuel

Decommissioning, Decontamination and Remediation (DD&R)

Safety analysis to underpin decommissioning process at facilities which have produced or used radioactive nuclear materials

Laboratory Testing & Software Capabilities

Bespoke testing and modeling services to validate analysis of DD&R processes

Nuclear Overview

Our Nuclear Services Group is recognized for comprehensive evaluations to help commercial nuclear power plants operate efficiently and stay compliant.

Severe Accident Analysis and Risk Assessment

Expert analysis of possible risk and consequences from nuclear plant accidents

Thermal Hydraulics

Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions

Environmental Qualification (EQ) and Equipment Survivability (ES)

Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions

Laboratory Testing & Software Capabilities

Testing and modeling services to support resolution of emergent safety issues at a power plant

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 (DSC/ARC supplies, CPA, C80, Super Stirrer)

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.

Vent Sizing Package 2


VSP2 Background

The Vent Sizing Package 2 (VSP2™) is the premier low thermal-inertia (low phi-factor) adiabatic calorimeter used for process hazard characterization. The VSP2 utilizes established DIERS technology to obtain critical safety data used to ensure safe process design. It is the commercial version of the original DIERS bench scale apparatus invented at FAI. We use the VSP2 every day in our fully equipped thermal hazards laboratory, and we also manufacture the instrument and support its use by colleagues around the world.

The VSP2 can be thought of as a bench scale chemical reactor contained within a protective containment vessel. Liquid or gaseous reactants can be added to (or withdrawn from) the test cell at any time during an experiment. Tests can be run in true adiabatic mode, with added external heating, or with external cooling. The cylindrical geometry of the test cell is ideal for reactions which require good agitation. Test cells are custom-made in a variety of materials and configurations to better simulate the process conditions.

VSP2 tests can be run in open cell mode (typical for very gassy systems) or in closed cell mode where the thin-walled test cell is kept intact by automatic pressure-balancing. Closed cell operation provides continuous pressure-temperature data during a runaway reaction, information which is necessary for detailed vent sizing calculations and which can be otherwise difficult to determine. Closed cell tests also require less post-test cleanup.

The sample size in the VSP2 (typically 80 ml) provides for a representative sample as well as good accuracy when adding ingredients that make up a small percentage of the mixture (e.g., catalyst additions). Temperature can be measured at up to three locations in the test cell, a useful option when testing solids or immiscible liquids. A baffled test cell with either a “star” stir-bar or a mechanical agitator can be used for optimal mixing of multiphase reactions, such as for emulsions, suspensions, or slurries. For true adiabatic operation (i.e., with low phi-factor and without externally imposed heating) the VSP2 is usually preferred. Polymer and multi-phase systems are particularly well suited to the VSP2 because of the excellent agitation and continuous vapor pressure measurement.


Its versatile and innovative design allows the VSP2 to simulate any number of upset (abnormal) conditions which might lead to a runaway chemical reaction (e.g., loss of cooling, loss of stirring, mischarge of reagents, mass-loaded upset, batch contamination, fire exposure heating, etc.). VSP2 data yield critical rates of temperature and pressure rise during a runaway reaction, thereby providing reliable energy and gas release rates which can be applied directly to full scale process conditions.

The VSP2 typically utilizes a sample size of 40-100 grams in a lightweight metal test cell with a volume of approximately 120 ml. The test cell is surrounded by a heater which is used to maintain adiabatic conditions during an experiment. This test cell and heater assembly is placed in a 4L containment vessel. Tests are typically performed as a closed system, so that vapor pressure data can be directly measured throughout the runaway.

VSP2wscreenVSP2 Benefits

The VSP2 represents Available Best Practice and has its roots in established DIERS technology which is recognized by OSHA as an example of good engineering practice. The VSP2 identifies and quantifies process safety hazards so they can be prevented or accommodated by process design. VSP2 data include adiabatic rates of temperature and pressure change which, due to the low thermal-inertia test design, can be directly applied to process scale to determine relief vent sizes, quench tank designs and other relief system design parameters related to process safety management.

Features and Applications

The versatile VSP2 design lets you directly simulate most process upset conditions including:

  • Loss of cooling or agitation
  • Accumulation or mischarge of reactants
  • Contamination of batch
  • Thermally initiated decomposition
  • Resident incubation time

Many testing configurations to accommodate a range of applications including:

  • Solids, liquids or two-phase mixtures
  • In-situ liquid/gas dosing or sampling
  • Closed or open (vented) tests
  • Scaled blowdown simulation
  • Two-phase flow regime determination
  • Test cells are available in 304 & 316 SS, Hastelloy C, Titanium and glass

VSP2 data allow you to completely characterize chemical reaction hazards and determine key process safety parameters including:

  • Required size of emergency relief system (ERS)
  • Adiabatic temperature and pressure rise rates (dT/dt, dP/dt)
  • Total adiabatic temperature rise (ΔTad)
  • Heat of reaction or mixing
  • Vapor pressure data
  • Time- to-maximum rate (TMR)
  • Temperature of no return (TNR)
  • Self-accelerating decomposition temperature (SADT)

Contact us to discuss your process safety applications and obtain a customized VSP2 quote.

VSP2 Resources & Guides

The Versatile VSP2
The VSP2 - is it Still Relevant? | Fauske and Associates
Using VSP2 to Perform Relief Sizing On Epichlorohydrin Chemistry
Vent Sizing (VSP2) User Forum – Optimizing Temperature Measurement
VSP2 Pressure Transducer Calibration & Maintenance Guide
VSP2 – Everything You Need to Know About Setting Up Your Heater Assembly