Fire Smoke and Gas: What Happens to You?

There are some unknown hazards in the fire that are closely related to the time, location, and how the smoke occurs. Understanding this knowledge will help firefighters avoid more potential hazards and protect their safety.

Recently, scientists have discovered in the research of the fire field some unimaginable dangers. These extra dangers are closely related to the time, location and how it affects the human body. In this article we will discuss these issues and, where possible, suggest improvements to prevent these hazards. Remember that the greatest risk to firefighters comes from their job, but it is virtually impossible to completely avoid all risks. Our goal is to discover these hidden risks so that firefighters can make more judgments based on knowledge to effectively control their own risks.

Toxic environment VS non-toxic environment and chronic exposure

The U.S. Occupational Safety and Health Administration (OSHA) environmental regulations show that IDLH ( immediately Dangerous to Life or Health concentration , ie, the concentration of air pollutants in the environment reaches a certain dangerous level, such as being fatal, permanently damaging to health, or The immediate loss of ability to escape will immediately threaten life. Any worker exposed to a hazardous environment needs to wear appropriate respiratory protective equipment. The SCBA ( Self-Contained Breathing Apparatus , which is a stand-alone breathing apparatus) is usually used in an active fire ( burning ) building within the current fire scene . In the environmental fire in the building, it can be detected to one or more gases, and lower than the recommended exposure limit to announce when non-IDLH (not reach the IDLH) level in a gas having a threat to the environment. In addition, the exterior of a fire building is generally considered a non-IDLH environment and is therefore not monitored. In a recent fire study, we chose Carmel , Indiana, where the internal structure of a building was burned but externally complete (as opposed to the 1403 training agreement ) . We monitor the external environment for carbon monoxide (CO) and hydrogen cyanide (HCN) . The monitors are set at 10 , 20 and 30 feet and placed in the four corners of the building. During the growth phase of the fire , HCN and CO concentrations were recorded in all aspects exceeding IDLH levels. This shows that monitoring should not only be carried out within the building, but also consider the external environment of the building.

Fire suppression work is assumed to be performed under non-IDLH conditions. Even if this assumption is valid , Lai said to the operator that there may still be a huge health threat to the environment. Single point of view from a single event, the level of exposure to low-pollution environment may appear out of the threat may be insignificant; however, for professional firefighters, long-term exposure to accumulate in the environment and may lead to the development of chronic diseases. This effect has emerged in other industries - long-term exposure to chronic , low-level environments is closely linked to heart , lung , and nervous system diseases.

Smoke composition

The main component of smoke produced during a building fire is a mixture of gas and tiny particles, which are harmful to human health. Research on the composition of smoke from building fires has been comprehensively studied (1) and will not be discussed extensively here. However, the most important thing is to be understood that while the qualitative component of smog may not have changed much, but in recent years, the proportion of the composition of the substance vary widely. With natural fibers and plastic materials are widely used in home and building, the large amounts of gas and smoke compounds present in relatively has changed. New building materials and textile fabrics have been confirmed to contain higher aldehydes and other toxic substances than building materials 30 years ago (2) .

Toxic gases harm the human body

Toxins enter the body into several paths , including ingestion, inhalation , infusion and absorption. In the fire , only inhalation and absorption are related to the skin. The lungs provide a place for exchange of inhaled gases with gaseous substances in the blood. Although the lungs are part of normal respiratory function to promote the exchange of oxygen and carbon dioxide , it also provides a way for toxic gases to enter the blood stream. The two main toxic gases, CO and HCN , produced in the fire field enter the human blood circulation through this route. CO is suffocating and its ability to bind to hemoglobin is 200 times that of oxygen . Therefore it eliminates the ability of systemic blood to deliver oxygen. HCN is also a suffocation-type substance that destroys the ability of cells to use oxygen to produce the energy needed by the body. Importantly, exposure to HCN often results in muscle hypoxia or even suffocation; more importantly , HCN and CO work together to attack the respiratory system from both the delivery and use of oxygen, which speeds up the death of the firefighter after poisoning. .

The process of absorbing toxic substances from the skin is much more complicated than the inhalation process. The skin can be seen as a two-tiered system - the stratum corneum (also known as the epidermis or the outer layer) is composed of a thin layer of dead cells, which is the main barrier to skin absorption of toxins. When a substance is deposited or in contact with the skin surface , a concentration gradient is established to drive the diffusion of toxic substances. Below the epidermis is a relatively thick layer of highly active tissue . The tissue contains blood vessels, sweat glands, hair follicles and nerves. The toxic substances absorbed by the skin are diffused through this layer of system. This relationship is described by Fick's Law of Diffusion . Essentially , how much material can reach the blood and cause toxic loads is determined by the characteristics of the compound and the tissue. Hydrophobic skin layer means that it is insoluble in water, therefore, similar to water-based compound will be hard to pass the skin layer; and an organic compound, such as solvents more easily through the epidermis. Gases , such as HCN and H2S, are more easily moved in the dermis and can promote toxic loads at moderate concentrations (4) . During exercise, a blood circulation well-defined skin complex area, the blood flow through the skin is also another factor leading to increased toxic load. When the skin heats , more blood flows to the skin and causes a gradient of diffusion of the contaminants.

A firefighter’s outer protective equipment provided reliable protection for part of his exposed skin during the fight. However, if it is in direct contact with external protective equipment that is continuously exposed to pollution sources and has not been carefully cleaned, it is also a source of toxic pollution.

Fick's law is the law describing the macroscopic mass diffusion phenomena, which is physiologist Fick (Fick) was discovered in 1855. Including two contents: ( 1 ) As early as 1855 , Fick proposed that: in the unit time, the flow of diffused material per unit area perpendicular to the diffusion direction (called diffusion flux , denoted by J ) and concentration gradient (concentration gradient) proportional to the cross-section at, say, the larger the concentration gradient, the greater the diffusion flux. This is Fick's first law. ( 2 ) Fick's second law is derived on the basis of the first law. Fick's second law states that in the non-steady state diffusion process, at the distance x , the rate of change of the concentration with time is equal to the negative value of the diffusion flux with the rate of change of the distance.

This article from the "fire front", author: reporter, Chinese rescue equipment network order.