Hazard Recognition

Some common hazards such as fire are easy to recognize. To recognize and determine other hazards usually requires training or classes that help you understand the nature and extent of these hazards. By reading and understanding the information enclosed here and also in DOT/NFPA, this information should be able to help you recognize and determine most common hazards. Some other hazards need instrumentation to determine the nature and severity of the hazard (i.e. Geiger counter or gas chromatograph). There are even some hazards that are indeterminate and may not even be immediately recognizable.

  • Fire & the Fire Triangle
  • Potential Hazards
  • Indeterminate Hazards
  • Health Effects
  • Exposure Guides
  • Routes of Entry
  • Noise

Fire & The Fire Triangle

The most basic hazard is fire. There are three elements required for combustion (fire) to occur. The elements required for combustion are: fuel, oxygen, and an ignition source. Sources of ignition may be physical (spark, small flame, cigarette, or a hot piece of equipment), or it may be chemical, such as an exothermic reaction.

The easiest and safest way to avoid fires or explosions when working with or storing flammables is by controlling the source of ignition.

The auto-ignition temperature is the temperature at which a material will spontaneously ignite. By knowing the auto-ignition temperature, fires can be avoided by keeping temperatures below the ignition point). For example, gasoline can spontaneously ignite when spilled onto an overheated engine or manifold.

Oxygen, the second requirement for combustion, is generally not limiting. Oxygen in air is sufficient to support combustion of most materials within certain limits. These limitations are compound-specific and are called the explosive limits in air.

Once a fire has started, control of the fire can be accomplished in several ways: Through water systems (by reducing the temperature), carbon dioxide, halon, or foam systems (by limiting oxygen), or through removal of the fuel (by shutting off valves or other controls).

The Flash point is defined as the minimum temperature required for a material to release enough vapors for form an ignitable mixture in air if a spark is provided. Another factor that relates to flammability is the vapor concentrations in air. The lowest concentration is called the Lower Explosive Limit (LEL). Concentrations lower than the LEL contain too little fuel; they are too "lean" to ignite. The Upper Explosive Limit (UEL) is the highest concentration that can support combustion. Levels above the UEL are too "rich" because the fuel is displacing the necessary amount of oxygen. The concentrations between the LEL and the UEL are considered to be the flammable range.

Potential Hazards

Incidents that require an emergency response can introduce multiple health and safety hazards, any one of which could result in serious injury or death. These hazards are a function of the different science disciplines that inhabit Duncan Hall and the Science buildings and the work routinely being performed in these buildings. Though not a science building, MacQuarrie Hall could encounter the last six items listed. The potential hazards that could be encountered in these buildings during an emergency situation include:

  • Chemical exposure
  • Biological hazards
  • Ionizing radiation
  • Fire and explosion
  • Safety hazards
  • Electrical hazards
  • Noise exposure
  • Extreme temperature stress
  • Oxygen deficiency

Indeterminate Hazards

This can consist of various situations where the nature or degree of hazard is questionable and/or difficult to ascertain after an initial examination. An example of this can be an unattended backpack in the hallway (or classroom, etc) or a suspicious package. These types of hazards and others can better be explained in the University Police Department's (UPD) Emergency Procedures Handbook that is available from the website: http://www.sjsu.edu/police/. Click on the Emergency Preparedness on the right hand side and you will then have a choice of Emergency Procedures Handbook and/or Family Safety Handbook. If you don't have Adobe Acrobat 9 (reader), you can download it (free) from http://www.adobe.com.

Health Effects

Health effects include hazards from chemical, biological and ergonomic exposures and hazards from physical effects from heat exposure, radiation and noise. All of these hazards can harm by injury or illness over a short and/or long term.

Chemical Hazards

A chemical is considered a poison when it causes harmful effects or interferes with biological reactions in the body. Only those chemicals that are associated with a great risk of harmful effects are designated as poisons. Most exposures are from inhalation of dusts, mists, fumes, vapors and gases or from absorption through the skin or eyes. The severity of the hazard depends on exposure length and the concentration of the chemical. The combination of these two factors determines the dose of the substance and will determine whether or not there will be an effect from the chemical exposure.

The effects of one chemical may be attenuated or accentuated by the interaction of another chemical. Small amounts of either chemical may not be harmful, but exposure to the combination of both chemicals may be harmful or dangerous.

A single, short exposure or a few exposures to (usually to a large dose) is termed an acute exposure. A repeated exposure over many months or years (usually to relatively lose doses) is termed chronic exposure. Acute effects are usually seen quickly.

When the body is affected at the point where a chemical contacts it, this is called a local effect. When the body is affected at some other place than the point of chemical contact, this is called a systemic effect. For example, a substance can be inhaled, but once in the body, the chemical substance affects the liver.

Biological Hazards

Most biological hazards are grouped under bloodborne diseases. Bloodborne diseases that you could potentially be exposed to on the job include Hepatitis (Includes A, B, C, D and E. Hepatitis causes inflammation of the liver (hepatitis literally means “inflammation of the liver”) with Hepatitis B being the most likely bloodborne disease that can be encountered on the job. ), human immunodeficiency virus (HIV) (also known as AIDS (Acquired Immune Deficiency Syndrome), syphilis and malaria. The three pathogens of most concern are HIV and Hepatitis (B) & (C). If you have any questions about bloodborne or communicable diseases, you can go to http://www.cdc.gov.

Ergonomic hazards

Ergonomics is about 'fit': the fit between people, the things they do, the objects they use and the environments they work, travel and play in. If a good fit is achieved, the stresses on people are reduced. They are more comfortable, they can do things more quickly and easily, and they make fewer mistakes.

So when we talk about 'fit', we don't just mean physical fit, we are concerned with psychological and other aspects too. That is why ergonomics is often called 'Human Factors'.

The goal of ergonomics is to design jobs to fit people. This means taking account of differences such as size, strength and ability to handle information for a wide range of users. Then the tasks, the workplace and tools are designed around these differences. The benefits are improved efficiency, quality and job satisfaction. The costs of failure include increased error rates and physical fatigue - or worse.

Even the simplest of products can be a nightmare to use if poorly designed. Our ancestors didn't have this problem. They could simply make things to suit themselves. These days, the designers of products are often far removed from the end users, which makes it vital to adopt an ergonomic, user-centered approach to design, including studying people using equipment, talking to them and asking them to test objects. This is especially important with 'inclusive design' where everyday products are designed with older and disabled users in mind.

Ergonomic issues can be brought up to Risk Management (previously known as Environmental Health and Occupational Safety) at 924-2150.

Exposure Guides

Personal Exposure Guides: Personal exposure guides are indications that hazardous conditions may exist. Watch for the following personal signs of exposure to toxic chemicals. If any of these occur, leave the site and report the problem immediately. Do NOT return until a qualified person has checked out the cause of the symptoms.

Six warning signs of chemical exposure:

  1. Breathing difficulties Ð breathing faster or deeper, soreness and a lump in the throat.
  2. Dizziness, drowsiness, disorientation, difficulty in concentration.
  3. Burning sensation in the eyes or on the skin, redness, or soreness.
  4. Weakness, fatigue, lack of energy.
  5. Chills, upset stomach.
  6. Odors and/ or a strange taste in your mouth.

OSHA guidelines require that you know the chemical to which you are being exposed. General guidelines often use short phrases, a word, numbers or symbols to communicate hazards such as "Avoid skin contact" or "Avoid breathing vapors." The general guidelines do not require that you know the amount of chemical present or its concentrations in the air. These are often found on labels or placards on chemical containers.

Routes of Entry

Chemical substances can enter the body through inhalation, ingestion and absorption (through eyes and skin). Another possible method of entry is from punctures. Many substances have more than one route of entry.


Inhaled contaminants that adversely affect a person fall into three categories:

  1. Aerosols and dusts: when aerosols and dusts are deposited in the lungs, they may produce tissue damage, tissue reaction, disease, or the physical stoppage of air sacs in the lungs.
  2. Corrosive gases: corrosive gases cause damage to the lung tissues, such as burns or scarring.
  3. Toxic aerosols or gases: toxic aerosols or gases do not affect the lung tissues, but are passed directly into the blood stream. Once in the blood stream, they are carried to other organs and/or they affect the blood's ability to carry oxygen.


Eating or drinking contaminated food is how toxic materials can be ingested. Once in the gastrointestinal tract, toxic chemicals can then be absorbed into the blood stream. Inhaled toxic dusts can also be ingested in amounts large enough to cause poisoning. Ingestion toxicity is normally lower than inhalation toxicity for the same material, due to the relatively poor absorption of many chemicals from the gastrointestinal tract into the blood stream.


The skin is the largest organ on the body and upon contact with a substance, five scenarios are possible:

  1. The skin and its associated layer of fat (lipid) cells act as an effective barrier against penetration, injury, or other forms of irritation.
  2. The substance reacts with the skin surface and causes primary irritation (dermatitis).
  3. The substance penetrates the skin and accumulates in the tissue, resulting in allergic reactions (skin sensitization).
  4. The substance penetrates the skin, enters the bloodstream and acts as a poison to other body parts (systemic action).
  5. The substance penetrates the skin, dissolving the fatty tissues, and allows other substances to penetrate the skin layers.


Chemicals or biological agentscan be introduced into the body through punctures such as nails or syringes.

Skin absorption is not the same for every part of your body. Different parts of the body absorb chemicals at very different rates


Noise Levels and Frequency

Sound can be measured scientifically in two ways. Intensity, or loudness of sound, is measured in decibels. Pitch is measured in frequency of sound vibrations per second.


Intensity of sound is measured in decibels (dB). The scale runs from the faintest sound the human ear can detect, which is labeled 0 dB, to over 180 dB, the noise at a rocket pad during launch. Decibels are measured logarithmically. This means that each increase is 10 times the lower figure. Thus, 20 decibels is 10 times the intensity of 10 decibels, and 50 decibels is 10,000 times as intense as 10 decibels. Each 5 decibels increase doubles the loudness in your ear. For example, being exposed to a 90-decibel noise for eight minutes is equivalent to being exposed to a 95-decibel noise for four minutes.

A noise level above 125 decibels can be painful. Obviously, noise at this level can cause damage to your hearing. Experts agree that continued exposure to noise above 85 dBA over time, will cause hearing loss. But more importantly, noise levels between 85 and 125 decibels can cause "painless" hearing damage -- damage that you may not be aware of at the time, but that can be causing permanent damage to your inner ear. To know if a sound is loud enough to damage your ears, it is important to know both the loudness level (dBA) and the length of exposure to the sound. In general, the louder the noise, the less time required before hearing loss will occur. According to the National Institute for Occupational Safety and Health (1998), the maximum exposure time at 85 dBA is 8 hours. At 110 dBA, the maximum exposure time is one minute and 29 seconds.


Frequency is measured in cycles per second, or Hertz (Hz). The higher the pitch of the sound correlates to a higher frequency. Human speech, which ranges from 300 to 4,000 Hz, sounds louder to most people than noises at very high or very low frequencies. When hearing impairment begins, the high frequencies are often lost first, which is why people with hearing loss often have difficulty hearing the high pitched voices of women and children.

Frequency is important because higher frequency noise can cause more damage to the hair cells in the inner ear. So, even though a high-frequency noise may only have a loudness of 85 dBA, it can cause more damage than a low-frequency noise that has a loudness of 95 dBA.

Loss of high frequency hearing also can distort sound, so that speech is difficult to understand even though it can be heard. Hearing impaired people often have difficulty detecting differences between certain words that sound alike, especially words that contain S, F, SH, CH, H, or soft C, sounds, because the sound of these consonants is in a much higher frequency range than vowels and other consonants.

Noise Exposure in the Workplace

There are two major types of noise in the workplace:

  1. Continuous noise is defined as noise whose highest levels occur more often than once per second.
  2. Impulse, which is sharp outbursts of noise. Impulsive noise is assumed to have peaks occurring less often than once a second, and is limited to peak sound pressure levels of 140 dB.

Both types of noise can be harmful, depending on how loud the noise is and how long you are exposed to the noise.

The best way to reduce worker's noise exposure is to:

  1. Eliminate the source of the noise.
  2. Isolate the noise from reaching people.
  3. Minimize the time of exposure.

Maximum work duration in different noise levels:

Duration per Day (hours) Sound Level dB(A) Slow Response
8 90
6 90
4 95
3 97
2 100
1.5 102
1 105
0.5 110
0.25 or less 115

Points of Reference (measured in dBA or decibels):

  • 0 The softest sound a person can hear with normal hearing.
  • 10 Normal breathing.
  • 20 Whispering at 5 feet.
  • 30 Soft whisper.
  • 50 Rainfall.
  • 60 Normal conversation.
  • 110 Shouting in ear.
  • 120 Thunder.