Accident Investigation Techniques

OSH 4308, Advanced Concepts in Environmental Safety Management 1

Course Learning Outcomes for Unit II Upon completion of this unit, students should be able to:

1. Evaluate safety, health, and environmental hazards in the workplace. 1.1 Identify the various types and uses of ventilation measuring equipment, including pitot tubes,

rotating vane anemometers, and thermal anemometers.

4. Perform appropriate calculations regarding the measurement, evaluation, and control of safety, health, and environmental hazards. 4.1 Calculate a worker’s exposure to particulates and gases using the time-weighted average

equation. 4.2 Determine employee exposure by utilizing various equations for gaseous and liquid mixtures. 4.3 Contrast the different types of ventilation, including general, dilution, and exhaust ventilation.

7. Explain scientific facts and concepts that impact the occupational safety and health professional.

7.1 Examine chemistry’s importance to occupational safety and the health professional.

Course/Unit Learning Outcomes

Learning Activity

1.1 Unit II Project

4.1 Unit II Project

4.2 Unit II Project

4.3 Unit II Quiz

7.1 Unit II Quiz, Unit II Project

Reading Assignment Chapter 4: Particulates and Gases Chapter 7: Ventilation

Unit Lesson The purpose of this unit is to provide you with the knowledge required to calculate employee exposures to particulates and gases and to evaluate the mechanical ventilation systems used to control these contaminants. Whether we are talking about an employee who is about to enter a permit-required confined space where H2S is potentially present at levels >10 ppm (parts per million) or a welder exposed to >10 mg/m3 (milligrams per cubic meter) of iron oxide fumes, safety professionals must be knowledgeable in the control and remediation measures that can and must be implemented to protect the health and safety of employees. To reduce or eliminate any hazard from the work area, there are three methods that the safety professional must adhere to. These methods include engineering control, administrative control, and personal protective equipment. As we all know, the best and most permanent method of control is engineering controls. When we discuss engineering controls of particulates and gases, we are primarily talking about ventilation.

UNIT II STUDY GUIDE

Particulates, Gases, and Ventilation

OSH 4308, Advanced Concepts in Environmental Safety Management 2

UNIT x STUDY GUIDE

Title

Permissible Exposure Limits In order to fully appreciate the need for ventilation, you must first have an understanding of particulates and gases and how they react with other chemicals and how employee exposures to these particulates and gases are measured. We begin by stating that Permissible Exposure Limits (PELs) are the only legally-enforceable standard for employee exposure. PELs are based on an eight-hour workday. This would be a great standard if everyone worked eight hours per day. However, many companies work eight, ten, or twelve hours per day. Do we still use the eight-hour PEL for these times? The obvious answer is no. When we have employees who may be exposed to various contaminants (i.e., respirable dust, which has a PEL of 5 mg/m3), what would the twelve-hour PEL be? To modify the PEL, we utilize the following equation:

𝑃𝐸𝐿12−ℎ𝑜𝑢𝑟 = 𝑃𝐸𝐿8−ℎ𝑜𝑢𝑟 𝑥 8 ℎ𝑜𝑢𝑟𝑠

12 ℎ𝑜𝑢𝑟𝑠

= 𝑃𝐸𝐿12−ℎ𝑜𝑢𝑟 = 5.0

𝑚𝑔 𝑚3

𝑥 8 ℎ𝑜𝑢𝑟𝑠

12 ℎ𝑜𝑢𝑟𝑠

= 𝑃𝐸𝐿12−ℎ𝑜𝑢𝑟 = 3.33 𝑚𝑔/𝑚

3 Time-Weighted Averages Time-weighted averages (TWAs) is the concentration of an employee’s exposure to certain elements for a specified period of time, and it depends on the various concentrations for a period of time over an eight-hour, ten-hour, or twelve-hour period. To calculate TWA, collect an actual sample of the air for specific time periods and use the following equation:

𝑇𝑊𝐴 = 𝐶1𝑇1 + 𝐶2𝑇2 + ⋯ 𝐶𝑛𝑇𝑛 𝑇𝑜𝑡𝑎𝑙 ℎ𝑜𝑢𝑟𝑠 𝑤𝑜𝑟𝑘𝑒𝑑

Then, compare the outcome of the sample TWA to the PEL, which can be found in Table Z-1 of 29 CFR 1910.1000.

WebQuest Take a few minutes to go to www.osha.gov and review the details of PEL in Table Z-1 of 29 CFR 1910.1000.

The Primary Purposes of Ventilation One method of achieving engineering controls, in relation to particulates and gases, is the use of ventilation. The primary purposes for using ventilation is to (1) maintain adequate oxygen; (2) control hazardous concentrations of chemicals; (3) remove odors; (4) control humidity and temperature; and (5) remove contaminants at the source, before they enter the workplace. By understanding how to use and control ventilation, safety professionals can successfully eliminate, or greatly reduce, any concentration of contaminant in the air. Three Categories of Ventilation Ventilation is divided into three categories, and they are: general, dilution, and local exhaust ventilation (Yates, 2015). General ventilation is primarily used for comfort, such as temperature, humidity, and odor control. Dilution ventilation is used to control contaminants of moderate toxicity, which result from a large number of sources, where there is intermittent exposure and the emission sources are well distributed. The elements of a dilution system include source of exhaust air, source of air supply, a duct system, and a method to filter and temper incoming air. The last type of system to be discussed is local exhaust ventilation, which is designed to control contaminants at the source before they mix with breathing air. Local exhaust ventilation is selected to control highly toxic substances from a single source emission and one that has direct employee exposures. Examples of local exhaust include welding exhaust systems, grinding exhaust systems, or automotive (inside) exhaust systems. One specific note of concern, when designing local exhaust systems is that energy is required to move air. Air is constantly turbulent and moves at 25 feet per minute (fpm).

OSH 4308, Advanced Concepts in Environmental Safety Management 3

UNIT x STUDY GUIDE

Title

General Ventilation Dilution Ventilation

Local Exhaust Ventilation

Purpose Comfort (i.e., temperature, humidity, and odor control)

 Control contaminants of moderate toxicity

 Control a large quantity of sources

 Control intermittent exposures

 Control locations with well- distributed emissions sources

 Control highly toxic substances

 Control single source emissions

 Control direct worker exposures

Examples Air conditioning and heating system in a home

Fire Departments and persons working in a confined space utilize a forced blower unit (to blow fresh air and mix it with contaminated air, thereby diluting the contaminated air)

 Welding exhaust systems

 Grinding exhaust systems

Purposes and examples of ventilation categories (Yates, 2015, pp. 247-248)

Reference Yates, W. D. (2015). Safety professional’s reference and study guide (2nd ed.). Boca Raton, FL: CRC Press.

Suggested Reading Navigate to the syllabus and review “Overview of the Projects in each unit.”

Learning Activities (Nongraded) Nongraded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information. Review the following questions as you prepare for the Quiz and Project in this unit.

1. Describe, in detail, the various types of ventilation, their particular design uses, and types of contaminants that are moved.

2. Discuss, in detail, the types and uses of local exhaust systems. 3. What are the three types of ventilation measuring instruments and describe their specific features and

what they measure. 4. Discuss, in detail, the importance of standard temperature and pressure (STP) and the different

STP’s and which one is used in ventilation. 5. Discuss, in detail, the differences in permissible exposure limits (PELs) and threshold limit values

(TLVs) in regards to employee exposures.