Forensic Engineers and Consultants

Archive: Fires and Explosions

Stop or I’ll Soot!!!

Fire. Something about fire touches our brainstems…both good and bad!  Uncontrolled fire is terrifying and deadly to be sure.  But the controlled burning of wood at a campfire or in a fireplace in your home almost can’t be beat, to my mind! For that very reason, a fairly common amenity to houses nowadays is the gas log fireplace insert.

When not installed properly, these logs will generate soot. These soot particles can leave the fireplace and meander.  All. Over. Your. House.  Literally, if enough soot gets into the HVAC system, you can have soot in every room.  If the logs soot badly, you will notice right away and correct the problem.  It’s when the logs produce lesser amounts of soot that it will build up so slowly as to not be noticeable.  That is, until you adjust a picture frame and notice how dingy the wall has become.

It can cost tens of thousands of dollars to clean soot from a home.  Soot removal is a specialized restoration service that a typical homeowner cannot provide for themselves. Where there is soot, there is also carbon monoxide which can cause a host of physical ailments, as well. Prolonged exposure to soot can unleash a host of breathing problems, including asthma, bronchitis, and respiratory infections.

Fire Place with Gas LogsFigure 1: Properly aligned logs in a gas burning fireplace allow for a much better ambiance.

Why does this happen? Remember that combustion is a chemical reaction at its roots.  The clean, or complete, combustion you want in a furnace or stove results in that quintessential ‘blue’ flame. And in those applications, that is exactly the desired result; maximum efficiency and heat for heat transfer.  However, if the fuel-to-air ratio is modified, you can bring some yellow to the party and have a gas flame appear more like the flames generated by a wood fire. Still, the yellow Bunsen burner doesn’t draw you to sit down to bask in its output, does it?

Bunsen Burner

Figure 2.  Different fuel-to-air ratios dictate flame color in a decidedly unromantic Bunsen burner

Hence the gas log fireplace insert.  At the heart of it, a typical gas log fireplace insert is a burner that has the proper fuel-to-air ratio for either natural gas or propane to produce the yellow flame similar to a wood fire.  They also have ceramic ‘logs’ that are placed around the burner to further mimic the look of said wood fire.

The proper placement of the faux logs is critical to the safe operation of the fireplace, however.  From the front, the logs give the appearance of a stack of wood.  If you inspect the set from the top, however, the area around and above the burners is free from objects.  If the logs are not properly placed or get knocked out of place and get in the way of the flame from the burner, then impingement occurs.  The flame impinging on the ceramic log will cause soot to form.

Soot on a ceramic log placed improperly - WarrenFigure 3:  Soot on a ceramic log that was placed improperly. This condition can cause soot to spread throughout the house.

Therefore, when installing a gas fireplace insert follow the log placement instructions carefully!  If there is no glass in between the logs and whatever room they are in, it’s also not a bad idea to check the log placement when doing annual maintenance on your fireplace insert.

Jennifer Morningstar, PE, CFEI, has 19 years of industrial experience. Her areas of emphasis include chemical release & exposure, OSHA process safety management, industrial accident investigation, fires & explosions, and scope of damage/cost to repair analyses. She spent 16 years working at a polyethylene terephthalate (PET) manufacturer.  She is an OSHA-trained Process Hazard Analysis study leader and completed Root Cause Failure Analysis training to become an Incident Investigator. Jennifer authored procedures for lockout/tagout and confined space entry. She has experience as an energy management consultant in a variety of industries including mineral extraction, pulp & paper, animal harvesting & packaging (including rendering) and grain milling.  Jennifer holds a Bachelor of Science Degree in Chemical Engineering from Virginia Polytechnic Institute and State University as well as a Masters of Business Administration from the University of South Carolina.

Electric Hazard Guardrail photo

Hazards Can Lurk Anywhere … Watch Your Step …

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While on a lunch stop during a recent vacation trip through Tennessee, I happened across a safety hazard that required immediate attention.  The establishment had a raised concrete patio at the front with a steel railing around the perimeter.  At one edge of the patio was a set of stairs with a continuation of the steel railing used as a handrail.  The top edge of the patio had light strings wrapping the top metal bar as accent lighting for the perimeter.  The light string continued down the stair handrail wrapped in the same manner as the rest of the patio. Read More

Gas Appliance testing lab

Testing As Part of Gas Appliance Incident Investigation

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Equipment and appliances supplied with fuel gases like natural gas, propane and butane are a common and convenient part of most of our lives.  Such devices as gas grills and ranges, ovens, furnaces, space heaters and water heaters usually perform without incident.  However, when they malfunction the potential for incidents such as fires and explosions, carbon monoxide (CO) poisoning and burn injuries may occur. These incidents may be due to design and manufacturing defects in the product, or improper installation or operation of the device.

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Under the sink chemicals

Not Your Father’s House Fire

Remember the good old days when our homes were built with only lumber, dry-wall, and roofing?   Me neither.  However, we talk about ‘modern’ construction materials like this is a new phenomenon.  The truth is ‘modern’ construction materials started sneaking into homes over fifty years ago.  It’s not only construction materials that have changed: a century ago, we furnished our houses with wood, cloth, metal, and glass. Today, it’s plastics, foams, and coatings.

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An example of a process flow diagram

OSHA’s Process Safety Management – Is This Process Covered?

In February of 1992, the OSHA Process Safety Management (PSM) standard was issued. The official title is: ‘Process Safety Management of Highly Hazardous Chemicals.’ As its title implies, not every facility is covered by this rigorous standard. A process must contain highly hazardous, as defined by OSHA, chemicals above a certain weight threshold, again defined by OSHA. Notice that this is a process by process determination, so there could be certain processes at a manufacturing facility that are not covered by this standard situated beside other processes that are.
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A corroded boiler tube

Boiler Blowdown – It’s Not a Dance Move

When thinking about the safe operation of boilers (and don’t we all?), several systems can readily be named; flame control, fuel/air ratio; steam pressure control, levels in the vessel, etc. What about the water? It seems so passive, as long as there is enough for level control, what’s the big deal? Well, it turns out, that as the steam produced by a boiler is used in the process, the condensate from that steam is returned to the boiler as feedwater. However, since 100% of the condensate is not returned, whatever solids had been in that water before it evaporated to form steam are left in the remaining water.  Fresh feedwater is added to maintain levels, but even fresh water contains some dissolved solids. So over time, the water in the boiler system gets saturated with all sorts of dissolved minerals.
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Cooker - Figure 2

Commercial Gas-Fired Cookers Can Do More Than Burn

The first hazard that comes to mind when thinking about large scale ovens and steam kettles is burning or scalding injury. Carbon monoxide poisoning is just as dangerous but less understood, so oftentimes proper prevention methods are not followed. In the United States, this results in over 20,000 emergency room visits and over 400 deaths a year. Before we get to the case study and poisoning prevention methods, we need to know what CO is, where it comes from, and why it is poisonous. Read More

Fig-1-Chem-E-Intro

Chemical Engineers: More than Glorified Plumbers – Really!

As a senior at Virginia Tech, I was told that ChemE’s were little more than glorified plumbers.  Looking back, I’m pretty sure it was to keep our geek-egos in check. It was an effective tool! However, as I grew and traveled as a professional, it became an effective descriptor; applying to a larger scale and using a modifier or two for specific applications.  So, if you have a loss that falls into one of the categories below, a ChemE could be the expert you need. Read More

Figure 1:  A view of the improperly constructed fireplace alleged to have caused the subject fire. 
 The hearth extension has been largely consumed in the fire.

Improper Fireplace Construction: Testing the Impact of Non-Compliant Clearance to Combustibles

Author

As the weather turns cold, many people use fireplaces to provide supplemental heat. The warmth from a fireplace is a comfort and the aesthetics of a glowing fire are a pleasure.  However, there is nothing pleasurable about a residential house fire that results from an improperly built or used fireplace or chimney. Read More

Figure 2: A Webshare photograph from a scan captured from the safety of a balcony in the workshop. The scanner operator never had to climb directly above the forklift to create the shot in Figure 1. The Webshare user can pan, zoom, and measure from the photograph. The grey target icons represent other scan locations on the ground.

Another Dimension of Engineering, Part 2: Visual Demonstrations Can Clarify the Issue

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In our last post on 3D scanning, we introduced Warren’s new Faro Focus X 330 three dimensional scanner.  To recap, the Faro scanner combines three dimensional laser measurement with automated photography to capture 360-degree data from the real world. Potential applications include vehicle accident scenes and damaged vehicles, structural collapses, fire scenes, flood damage scenes, and machinery and equipment analysis, among others. In this post, we will highlight some of the outputs that can be created from the detailed data captured by the scanner. Read More

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