Study guide
18.2 Foundry Operations and Hot Work Fire Prevention
CIH Certified Industrial Hygienist Exam
Track your progress as you read
Finished sections get a check mark.
1 Chapter 1: The CIH Exam and How to Use This Guide
1.1 CIH Exam Format, Scoring, and Test-Day Logistics 1.2 Eligibility, Application Windows, Fees, and Certification Maintenance 1.3 The BGC Blueprint, Subject Areas, and a Calculation-First Study Plan
2 Chapter 2: Basic Science & Calculations
2.1 Gas Laws and Vapor Calculations 2.2 Unit Conversions: ppm, mg/m³, and Standard Temperature/Pressure 2.3 Fluid Mechanics and Airflow Fundamentals
3 Chapter 3: Air Sampling & Instrumentation
3.1 Active and Passive Air Sampling Strategies 3.2 Particulate and Aerosol Sampling 3.3 Direct-Reading Instruments and Calibration
4 Chapter 4: Analytical Chemistry & Lab Methods
4.1 Gas Chromatography and Mass Spectrometry 4.2 High-Performance Liquid Chromatography and Ion Chromatography 4.3 Spectroscopy and Elemental Analysis 4.4 Gravimetric, Microscopy, and Wet Chemical Methods 4.5 Laboratory Quality Assurance, Chain of Custody, and Desorption Efficiency
5 Chapter 5: Biostatistics & Epidemiology
5.1 Lognormal Distributions and Exposure Data Statistics 5.2 Upper Confidence Limits (UCL95) and Compliance Decision Rules 5.3 Epidemiological Study Designs and Measures of Association 5.4 Sampling Strategy: Sample Size, Power, and Worker Selection
6 Chapter 6: Toxicology & Biological Monitoring
6.1 Dose-Response Relationships and Points of Departure 6.2 Toxicokinetics: Absorption, Distribution, Metabolism, and Elimination 6.3 Aerosol Deposition, Clearance, and Respiratory Tract Dosimetry 6.4 Hepatic, Renal, Neurologic, and Hematologic Target Organ Toxicity 6.5 Pulmonary Toxicology, Carcinogenicity, and Reproductive Hazards 6.6 OEL Frameworks, Classifications, and Excursion Limits 6.7 Chemical Mixtures and Extended Work-Shift OEL Adjustments 6.8 Biological Exposure Indices (BEIs) and Biomonitoring
7 Chapter 7: Biohazards & Indoor Environmental Quality
7.1 Mold, Fungi, and Microbial Contaminants 7.2 Infectious Agents, Bloodborne Pathogens, and Biosafety Levels 7.3 Indoor Environmental Quality (IEQ) Investigations 7.4 Sanitation, Potable Water, and Personal Hygiene Programs
8 Chapter 8: Community Exposure & Environmental Health
8.1 Clean Air Act Framework, NAAQS, and New Source Review 8.2 Hazardous Air Pollutants, CEMS, and EPA Reference Methods 8.3 Atmospheric Stability, Lapse Rates, and Plume Morphology 8.4 Gaussian Plume Modeling, Plume Rise, and Environmental Fate 8.5 HAZWOPER Scope, Mandates, and Training Tiers 8.6 Protection Levels, Site Zoning, Incident Command, and Decontamination 8.7 Water Pollution, Hazardous Waste, and Community Right-to-Know
9 Chapter 9: Health Risk Analysis & Hazard Communication
9.1 GHS Hazard Classification: Health and Physical Hazard Criteria 9.2 GHS Labels, Safety Data Sheets, and Trade Secret Rules 9.3 The AIHA Exposure Assessment Strategy and Similar Exposure Groups 9.4 Qualitative Exposure Profiling and the AIHA Risk Matrix 9.5 Quantitative Health Risk Characterization: HQ, HI, and ELCR 9.6 NIOSH Occupational Exposure Banding 9.7 Risk Communication and Reporting to Affected Parties
10 Chapter 10: Industrial Ventilation Principles & LEV Design
10.1 Elimination, Substitution, Isolation, Containment, and Process Change 10.2 LEV Hood Taxonomy and Capture Velocity Selection 10.3 Hood Airflow Equations, Entry Losses, and Hood Static Pressure 10.4 Particulate Transport Aerodynamics and Duct Sizing 10.5 Duct Friction, Fitting Losses, and System Balancing 10.6 Fan Categories and Pressure Dynamics Across the Fan 10.7 System Curves, the Fan Laws, and Density Corrections
11 Chapter 11: General Ventilation, Air Cleaning & Diagnostics
11.1 Dilution Ventilation Principles and Steady-State Modeling 11.2 Transient Purging and Air Distribution Geometry 11.3 Particulate Air Cleaning: Cyclones, Baghouses, Scrubbers, and ESPs 11.4 Gaseous Emission Control and Air Cleaner Selection 11.5 Ventilation System Troubleshooting and Testing
12 Chapter 12: Noise Measurement & Hearing Conservation
12.1 Acoustic Physics and Decibel Mathematics 12.2 Sound Propagation, Octave Bands, and Frequency Weighting 12.3 Noise Dose Metrics and OSHA versus ACGIH Criteria 12.4 Exchange Rates, Extended Shifts, and Dosimetry Field Protocols 12.5 Engineering Noise Controls and Hearing Protector Attenuation 12.6 Hearing Conservation Programs and Standard Threshold Shifts 12.7 Hand-Arm and Whole-Body Vibration
13 Chapter 13: Thermal Stress Assessment & Control
13.1 Wet Bulb Globe Temperature (WBGT) and Heat Stress Indices 13.2 Heat-Related Disorders, Acclimatization, and Work/Rest Regimens 13.3 Cold Stress Evaluation and Wind Chill
14 Chapter 14: Ionizing Radiation Protection
14.1 Ionizing Radiation Physics and Radioactive Decay Kinetics 14.2 Radiation Units, Radiobiology, and Health Effects 14.3 ALARA, Stay-Time, and the Inverse Square Law 14.4 Shielding Physics, Material Selection, and Gamma Constants 14.5 Radiation Detection Instruments and Spectrometry 14.6 Personnel Dosimetry, Dose Limits, and Contamination Surveys
15 Chapter 15: Non-Ionizing Radiation & Laser Safety
15.1 The Non-Ionizing Spectrum and Static/ELF Field Exposures 15.2 Radiofrequency and Microwave Exposure: SAR, Standards, and Surveys 15.3 Ultraviolet, Visible, and Infrared Radiation Hazards 15.4 Laser Safety Classifications and Optical Density Calculations 15.5 Illumination, Lighting Design, and Visual Performance
16 Chapter 16: Non-Engineering Controls & Personal Protective Equipment
16.1 Respiratory Protection Programs and Assigned Protection Factors 16.2 Maximum Use Concentration, Oxygen Deficiency, and Breathing Air 16.3 Particulate Filters, Sorbent Cartridges, and Change Schedules 16.4 Respirator Fit Testing Protocols 16.5 Chemical Protective Clothing and Dermal Exposure Control
17 Chapter 17: Ergonomics & Workstation Design
17.1 Soft-Tissue Biomechanics and WMSD Pathophysiology 17.2 Ergonomic Risk Factors and Their Interaction Effects 17.3 The Revised NIOSH Lifting Equation 17.4 RULA, REBA, the Strain Index, and the ACGIH HAL TLV 17.5 Anthropometry and Workstation Geometry 17.6 VDT Workstations, Hand Tool Design, and Administrative Ergonomics
18 Chapter 18: Work Environments & Industrial Processes
18.1 Welding Fume Emissions, Metal Fume Fever, and Cr(VI)/Manganese Toxicology 18.2 Foundry Operations and Hot Work Fire Prevention 18.3 Vapor Degreasing, Pickling, Electroplating, and Cyanide Baths 18.4 Spray Coatings, Isocyanates, and Semiconductor Manufacturing 18.5 Confined Spaces and High-Hazard Industrial Operations 18.6 Asbestos, Lead, and Silica: Regulated Substance Programs 18.7 Abrasive Blasting and Surface Preparation
19 Chapter 19: IH Program Management & Professional Ethics
19.1 The BGC Code of Ethics: Canons and Enforcement 19.2 Professional Liability, Standard of Care, and Expert Testimony 19.3 Occupational Health & Safety Management Systems (ISO 45001, ANSI Z10) 19.4 Exposure Records Access and Medical Surveillance 19.5 OSHA Injury and Illness Recordkeeping and Enforcement
18.2 Foundry Operations and Hot Work Fire Prevention
Key Takeaways Explain This Topic AI
Foundry operations produce respirable crystalline silica at core making, moulding, shakeout, and abrasive cleaning, with shakeout typically the highest-exposure task.
Cupola and pouring operations generate carbon monoxide, and enclosed pouring pits can become oxygen-deficient confined spaces.
The 35-foot rule requires combustibles to be moved at least 35 feet from hot work, or shielded where movement is not possible, before a hot work permit is issued.
A fire watch must be maintained during hot work and for at least 30 minutes after completion, extended to 60 minutes under NFPA 51B.
Last updated: August 2026
Foundry Operations and Hot Work Fire Prevention
Foundries combine every hazard already covered — respirable silica, metal fume, carbon monoxide, heat stress, and noise — in a single process line, and hot work anywhere in a plant carries a fire and explosion risk governed by its own permitting standard.
1. Foundry Operations: Core Making, Molding, Pouring, and Shakeout
Foundries produce metal castings by pouring molten ferrous (iron, steel) or non-ferrous (aluminum, bronze, brass, magnesium) metals into refractory sand molds. +-------------------------------------------------------------------------+
- | FOUNDRY PROCESS SEQUENCE & KEY HAZARDS |
- +-------------------------------------------------------------------------+
- | |
- | [ 1. Pattern & Core Making ] |
- | Hazards: Phenol-formaldehyde, furfuryl alcohol, MDI isocyanates, |
- | tertiary amine gas catalysts (TEA, DMEA). |
- | |
- | ▼ |
- | [ 2. Sand Mold Preparation ] |
- | Hazards: Respirable crystalline silica (quartz), bentonite, |
- | sea coal / carbonaceous dust. |
- | |
- | ▼ |
- | [ 3. Melting & Molten Pouring (1,100°C - 1,600°C) ] |
- | Hazards: Extreme infrared radiation / heat stress, CO, SO2, |
- | metal fumes (Fe, Zn, Pb), binder pyrolysis VOCs / PAHs. |
- | |
- | ▼ |
- | [ 4. Cooling & Shakeout (Mechanical Vibratory Separation) ] |
- | Hazards: Extreme respirable crystalline silica (cristobalite / |
- | quartz), carbon monoxide (CO), extreme noise and shock. |
- | |
- | ▼ |
- | [ 5. Casting Cleaning, Shot Blasting, & Grinding ] |
- | Hazards: Respirable silica dust, metal dusts, hand-arm vibration, |
- | abrasive wheel burst hazards, high noise (> 100 dBA). |
- +-------------------------------------------------------------------------+
- Chemistry of Core and Mold Binder Systems
Cores (used to create hollow internal cavities in castings) require rigid chemical binders that cure rapidly and break down thermally ("collapsibility") after metal solidification:
Furan / Acid-Cured Binders: Furfuryl alcohol reacted with formaldehyde or urea, catalyzed by strong acids (sulfonic acids). Hazards: furfuryl alcohol vapors, free formaldehyde, sulfur dioxide (extSO2).
Phenolic Urethane / Cold-Box Systems:
Part 1: Phenol-formaldehyde polymer dissolved in aromatic solvents.
Part 2: Polymeric isocyanate (methylene diphenyl diisocyanate [MDI]).
Catalyst: Gaseous tertiary amines— triethylamine (TEA) or dimethylethylamine (DMEA) —blown through the sand core box to catalyze instantaneous polymerization.
Amine Catalyst Toxicology ("Blue-Gray Haze" / Glaucopsia): Inhaled or ocular exposure to triethylamine vapors causes intracellular swelling of the corneal epithelium (corneal edema), producing a transient condition known as glaucopsia ("blue haze" or halos around light sources). While completely reversible within several hours of cessation of exposure, it temporarily impairs vision and indicates inadequate local exhaust capture on core-curing machines.
Green Sand Molding: Consists of high-purity silica sand (extSiO2, 85--90%), bentonite clay binder (5--10%), water (2--5%), and sea coal (pulverized bituminous coal, 2--8%). Molten metal in contact with sea coal generates a reducing carbonaceous atmosphere that prevents metal oxidation and produces a smooth casting finish, but pyrolyzes into carbon monoxide (extCO) , methane, and polycyclic aromatic hydrocarbons ( PAHs , e.g., benzo[a]pyrene).
Shakeout and Abrasive Cleaning Hazards
Respirable Crystalline Silica: The intense thermal shock (> 1,400°C) from molten iron converts sand grains at the mold-metal interface into high-temperature silica polymorphs, specifically cristobalite and tridymite , which are significantly more fibrogenic than raw α-quartz.
Carbon Monoxide (extCO): Incomplete combustion of carbonaceous binders and sea coal generates extreme surges of extCO during pouring and shakeout (> 200--500 ppm in unventilated areas).
2. Hot Work Fire Prevention, Permitting, and the 35-Foot Rule
Under OSHA 29 CFR 1910.252(a) and NFPA 51B ( Standard for Fire Prevention During Welding, Cutting, and Other Hot Work ), hot work is defined as any operation involving electric arc welding, oxyfuel gas cutting, brazing, soldering, grinding, or thermal spraying capable of initiating fires or explosions. +-------------------------------------------------------------------------+
- | THE NFPA 51B / OSHA 35-FOOT RULE ENVELOPE |
- +-------------------------------------------------------------------------+
- | |
- | | <---------- 35 Feet (11 m) ----------> | |
- | +-------------------+-------------------+ |
- | | | | |
- | | | | |
- | - - -+ - - - - - - - - - o - - - - - - - - - +- - - |
- | | | [Hot Work] | | |
- | | | Arc/Torch | | |
- | | | | | | |
- | - - -+ - - - - - - - - - o - - - - - - - - - +- - - |
- | | | | |
- | | | | |
- | +-------------------+-------------------+ |
- | |
- | MANDATORY PROTOCOLS WITHIN THE 35-FOOT RADIUS: |
- | 1. Relocate all movable combustible materials >= 35 ft away. |
- | 2. If combustibles cannot be moved, protect with listed fire blankets, |
- | flame-retardant curtains, or metal shields. |
- | 3. Seal all floor openings, cracks, pipe penetrations, and duct drops. |
- | 4. Wet down combustible wooden floors and cover with wet sand/sheet metal.|
- | 5. Shut down conveyor systems that could transport sparks elsewhere. |
- | 6. Perform atmospheric monitoring (< 10% LEL) before & during work. |
- +-------------------------------------------------------------------------+
- Mandatory Operational Safety Requirements
Hot Work Permit System: A written permit signed by a designated Permit Authorizing Individual (PAI) must be issued before initiating hot work in non-designated areas. The permit certifies that the area has been inspected, combustibles protected, automatic sprinkler heads shielded without impairing coverage, and flammable vapor tests conducted.
Atmospheric Testing: Testing with a calibrated combustible gas indicator (CGI) must verify that the ambient flammable gas or vapor concentration is below 10% of the Lower Explosive Limit (< 10% LEL) . Hot work is strictly prohibited in explosive atmospheres.
Dedicated Fire Watch:
A trained, dedicated Fire Watch is mandatory whenever combustibles are within 35 ft, wall/floor openings expose combustibles in adjacent areas, or work is performed on sandwich walls containing combustible insulation.
The fire watch must be equipped with fully charged portable fire extinguishers, possess authority to immediately stop hot work, and be trained in sounding alarms.
Duration: The fire watch must be maintained throughout all hot work operations and for at least 30 to 60 minutes after hot work is completed to detect and extinguish smoldering embers.
- 3. Worked Step-by-Step Calculation Examples
- Worked Example 17.1.1: Hexavalent Chromium 8-Hour TWA and Regulated Area Evaluation
Problem: An industrial hygienist conducts personal air sampling on a welder fabricating 304-stainless steel vessels using SMAW (E308-16 electrode). The sampling pump ran at a calibrated flow rate of 2.0 L/min for a total duration of 420 minutes.
Analytical laboratory analysis (NIOSH Method 7300/7605 via ion chromatography) determined a total Cr(VI) mass of 3.78 µg on the PVC membrane filter.
The worker performed welding for 420 minutes and spent the remaining 60 minutes of the 8-hour (480 min) shift in a clean administrative office with zero Cr(VI) exposure.
Calculate:
The sampled concentration (Cs).
The 8-hour Time-Weighted Average (8-hr TWA) exposure.
Determine compliance with OSHA 29 CFR 1910.1026 regarding the PEL (5.0 µg/m³) and Action Level (2.5 µg/m³), and specify mandatory employer actions.
Solution Steps:
Calculate total sampled air volume (V): V = Q × t = 2.0 L/min × 420 min = 840 L V = Q \times t = 2.0\text{ L/min} \times 420\text{ min} = 840\text{ L} V = Q × t = 2.0 L/min × 420 min = 840 L V = 840 L 1 , 000 L/m 3 = 0.840 m 3 V = \frac{840\text{ L}}{1,000\text{ L/m}^3} = 0.840\text{ m}^3 V = 1 , 000 L/m 3 840 L = 0.840 m 3
Calculate concentration during the sampling period (Cs): C s = Mass Volume = 3.78 μ g 0.840 m 3 = 4.50 μ g/m 3 C_s = \frac{\text{Mass}}{\text{Volume}} = \frac{3.78\ \mu\text{g}}{0.840\text{ m}^3} = 4.50\ \mu\text{g/m}^3 C s = Volume Mass = 0.840 m 3 3.78 μ g = 4.50 μ g/m 3
Calculate the 8-hour TWA: TWA 8 -hr = C s × t s + C office × t office 480 min = 4.50 μ g/m 3 × 420 min + 0 × 60 min 480 min \text{TWA}_{8\text{-hr}} = \frac{C_s \times t_s + C_{\text{office}} \times t_{\text{office}}}{480\text{ min}} = \frac{4.50\ \mu\text{g/m}^3 \times 420\text{ min} + 0 \times 60\text{ min}}{480\text{ min}} TWA 8 -hr = 480 min C s × t s + C office × t office = 480 min 4.50 μ g/m 3 × 420 min + 0 × 60 min TWA 8 -hr = 1 , 890 μ g ⋅ min/m 3 480 min = 3.9375 μ g/m 3 ≈ 3.94 μ g/m 3 \text{TWA}_{8\text{-hr}} = \frac{1,890\ \mu\text{g}\cdot\text{min/m}^3}{480\text{ min}} = 3.9375\ \mu\text{g/m}^3 \approx \mathbf{3.94\ \mu\text{g/m}^3} TWA 8 -hr = 480 min 1 , 890 μ g ⋅ min/m 3 = 3.9375 μ g/m 3 ≈ 3.94 μ g/m 3
Regulatory Interpretation & Employer Actions:
PEL Comparison: 3.94 µg/m³ < 5.0 µg/m³ (The exposure is below the PEL ; no regulated area or engineering violation).
Action Level Comparison: 3.94 µg/m³ > 2.5 µg/m³ (The exposure exceeds the Action Level ).
Mandatory Requirements: The employer must:
Conduct periodic exposure monitoring at least every 6 months .
Provide medical surveillance to the employee (if exposed ≥ AL for ≥ 30 days/year).
Implement training and hazard communication specific to Cr(VI).
Worked Example 17.1.2: Local Exhaust Capture Velocity for Welding Fume Extractor
Problem: An industrial hygienist is specifying an exterior movable capture hood (flanged rectangular hood, dimensions W = 0.3 m, L = 0.4 m, hood area A = 0.12 m²) for a manual GTAW/SMAW bench.
The hood centerline is positioned at a distance X = 0.25 m from the weld arc.
According to ACGIH Industrial Ventilation Manual guidelines, capturing welding fumes in stagnant-to-slow room air requires a minimum capture velocity Vx = 0.50 m/s (100 fpm).
Using the standard DallaValle equation for a flanged exterior hood: Q = 0.75 ⋅ V x ⋅ ( 10 X 2 + A ) Q = 0.75 \cdot V_x \cdot (10 X^2 + A) Q = 0.75 ⋅ V x ⋅ ( 10 X 2 + A )
Calculate the required exhaust airflow rate (Q) in m³/s and m³/hr (or CFM).
Solution Steps:
Identify parameters:
- Vx = 0.50 m/s
- X = 0.25 m → X² = 0.0625 m²
- A = 0.12 m²
Calculate required volumetric flow rate (Q): Q = 0.75 × 0.50 m/s × ( 10 × ( 0.25 m ) 2 + 0.12 m 2 ) Q = 0.75 \times 0.50\text{ m/s} \times \left(10 \times (0.25\text{ m})^2 + 0.12\text{ m}^2\right) Q = 0.75 × 0.50 m/s × ( 10 × ( 0.25 m ) 2 + 0.12 m 2 ) Q = 0.375 × ( 10 × 0.0625 + 0.12 ) = 0.375 × ( 0.625 + 0.12 ) = 0.375 × 0.745 Q = 0.375 \times (10 \times 0.0625 + 0.12) = 0.375 \times (0.625 + 0.12) = 0.375 \times 0.745 Q = 0.375 × ( 10 × 0.0625 + 0.12 ) = 0.375 × ( 0.625 + 0.12 ) = 0.375 × 0.745 Q = 0.279375 m 3 / s ≈ 0.279 m 3 / s Q = 0.279375\ \text{m}^3/\text{s} \approx \mathbf{0.279\ \text{m}^3/\text{s}} Q = 0.279375 m 3 / s ≈ 0.279 m 3 / s
Convert to m³/hr and CFM: Q = 0.279375 m 3 / s × 3 , 600 s/hr = 1 , 005.75 m 3 / hr Q = 0.279375\ \text{m}^3/\text{s} \times 3,600\text{ s/hr} = \mathbf{1,005.75\ \text{m}^3/\text{hr}} Q = 0.279375 m 3 / s × 3 , 600 s/hr = 1 , 005.75 m 3 / hr Q = 0.279375 m 3 / s × 2 , 118.88 CFM m 3 / s = 592 CFM Q = 0.279375\ \text{m}^3/\text{s} \times 2,118.88\ \frac{\text{CFM}}{\text{m}^3/\text{s}} = \mathbf{592\ \text{CFM}} Q = 0.279375 m 3 / s × 2 , 118.88 m 3 / s CFM = 592 CFM
Conclusion: The ventilation system must deliver at least 592 CFM (1,006 m³/hr) of exhaust airflow to guarantee the requisite 100 fpm capture velocity at the welder's arc.