MONTEREY BAY UNIFIED AIR POLLUTION CONTROL DISTRICT 

REGULATION IV 

PROHIBITIONS

1 

8/15/12 Rule 400 (Visible Emissions) 

RULE 400 VISIBLE EMISSIONS 

(Adopted July 1, 1969; Revised April 26, 1995, June 18, 1997, March 22, 2000, October 15, 2003, 

December 15, 2004; and August 15, 2012.)

CONTENTS 

PART 1 GENERAL ........................................................................................................................2 

1.1 Purpose .........................................................................................................................2 

1.2 Applicability .................................................................................................................2 

1.3 Exemptions ...................................................................................................................2 

1.4 Effective Dates ..............................................................................................................4 

1.5 References .....................................................................................................................4 

PART 2 DEFINITIONS ..................................................................................................................4 

2.1 Abrasives Certified for Permissible Dry Outdoor Blasting ..........................................4 

2.2 Obscurant ......................................................................................................................4 

2.3 Opacity ..........................................................................................................................4 

2.4 Ringelmann Chart .........................................................................................................5 

2.5 Startup ...........................................................................................................................5 

2.6 Teepee Burner ...............................................................................................................5 

PART 3 REQUIREMENTS AND STANDARDS ..........................................................................5 

3.1 General Visible Emission Limitations ..........................................................................5 

3.2 Industry-Specific Visible Emission Limitations ...........................................................6 

PART 4 ADMINISTRATIVE REQUIREMENTS .........................................................................7 

4.1 Test Methods ................................................................................................................7 
MONTEREY BAY UNIFIED AIR POLLUTION CONTROL DISTRICT 

REGULATION IV 

PROHIBITIONS

2 

8/15/12 Rule 400 (Visible Emissions) 

PART 1 GENERAL 

1.1 Purpose 

The purpose of this Rule is to provide limits for the visible emissions from sources 

within the District. 

1.2 Applicability 

The provisions of this Rule shall apply to all sources of air pollutant emissions in the 

District. 

1.3 Exemptions 

The provisions of this Rule shall not apply to the following activities: 

1.3.1 any open burning performed in compliance with Rule 438 {California Health and 

Safety Code (HSC) Sections 41704 (a), (b), (c), and (e)}; 

1.3.2 use of any aircraft to distribute seed, fertilizer, insecticides, or other agricultural aids 

over lands devoted to the growing of crops or raising of fowl or animals {HSC 

Section 41704 (d)}; 

1.3.3 agricultural operations necessary for the growing of crops or raising of fowl or 

animals {HSC Sections 41704 (g) and (h)}; 

1.3.4 the use of visible emission generating equipment in training sessions conducted by 

governmental agencies necessary for certifying persons to evaluate visible emissions 

for compliance with applicable District rules and regulations {HSC Section 41704 

(l)}; 

1.3.5 emissions from vessels using steam boilers during emergency boiler shutdowns for 

safety reasons, safety and operational tests required by governmental agencies, and 

where maneuvering is required to avoid hazards {HSC Section 41704 (j)}; 

1.3.6 emissions from vessels during a breakdown condition, as long as the discharge is 

reported in accordance with District requirements {HSC Section 41704 (k)}; 

1.3.7 smoke emissions from teepee burners during the disposal of forestry and agricultural 

residues or forestry and agricultural residues with supplementary fossil fuels when 

the emissions result from the startup or shutdown of the combustion process or from 
MONTEREY BAY UNIFIED AIR POLLUTION CONTROL DISTRICT 

REGULATION IV 

PROHIBITIONS

3 

8/15/12 Rule 400 (Visible Emissions) 

the malfunction of emission control equipment. This exemption does not apply to 

emissions which exceed a period or periods of time aggregating more than 30 

minutes in any 24 hour period, nor to emissions which result from the failure to 

operate and maintain in good working order any emission control equipment {HSC 

Section 41704 (m)}; 

1.3.8 smoke emissions from burners used to produce energy and fired by forestry and 

agricultural residues with supplementary fossil fuels when the emissions result from 

the startup or shutdown of the combustion process or from the malfunction of 

emission control equipment. This exemption does not apply to emissions which 

exceed a period or periods of time aggregating more than 30 minutes in any 24 hour 

period, nor to emissions which result from the failure to operate and maintain in 

good working order any emission control equipment {HSC Section 41704 (n)}; 

1.3.9 emissions from methanol fuel manufacturing plants which manufacture not more 

than 2,000,000 gallons of methanol fuel per day from wood, agricultural waste, 

natural gas, or coke (exclusive of petroleum coke). As used in this Subsection, 

"manufacturing plant" includes all necessary support systems, including field 

operations equipment that provide feedstock. However, this exemption shall be 

available to only one methanol fuel manufacturing plant in the District, and is 

effective only when the District is designated as an "attainment area" pursuant to the 

Federal Clean Air Act (42 U.S.C. Sec. 7401 et seq.) This exemption shall remain in 

effect with respect to a plant until five years after construction of the plant and shall 

have no force and effect with respect to the plant on and after that date {HSC 

Section 41704 (o)}; 

1.3.10 the use of an obscurant for the purposes of training military personnel and the testing 

of military equipment by the United States Department of Defense on any military 

reservation {HSC Section 41704 (p)}; 

1.3.11 wet plumes where the presence of uncombined water is the only reason for the 

failure of an emission to meet the limitations of Section 3.1 of this Rule. The burden 

of proof which establishes the application of this exemption shall be upon the person 

seeking to benefit from its provisions; 

1.3.12 the use of an orchard, field crop, or citrus grove heater which does not produce 

unconsumed solid carbonaceous material at a rate in excess of that allowed by State 

law, which is 1 gram per minute of unconsumed solid carbonaceous material. {HSC 

Sections 41704 (f) and 41860} 
MONTEREY BAY UNIFIED AIR POLLUTION CONTROL DISTRICT 

REGULATION IV 

PROHIBITIONS

4 

8/15/12 Rule 400 (Visible Emissions) 

1.4 Effective Dates 

This Rule, as most recently revised, is effective on August 15, 2012. 

1.5 References 

1.5.1 The requirements of this Rule arise from the provisions of: California Health & 

Safety Code Sections 39043.5, 41701.5, 41701.6, 41704 and 41860; Title 17 Section 

92000 et seq. of the California Code of Regulations, and the Code of Federal 

Regulations (CFR) Part 60, Part 61, and Part 63. 

1.5.2 Other related rules include: Rule 403 (Particulate Matter), Rule 404 (Sulfur 

Compounds and Nitrogen Oxides), Rule 423 (New Source Performance Standards), 

Rule 424 (National Emission Standards for Hazardous Air Pollutants), and Rule 438 

(Open Outdoor Fires). 

PART 2 DEFINITIONS 

2.1 Abrasives Certified for Permissible Dry Outdoor Blasting 

The abrasive blasting material defined in Title 17 of the California Code of Regulations 

Sections 92000 et seq. 

2.2 Obscurant 

Fog oil released into the atmosphere during military exercises which produces a smoke 

screen designed to eliminate the detection of persons or objects by visual or electronic 

means of observation within a localized area. {HSC Section 39043.5} 

2.3 Opacity 

The degree to which light is prevented from passing through an emission plume. Its 

measure is expressed as one (1.0) minus the optical transmittance of a smoke plume, 

screen target, etc. as determined by the test methods in Section 4.1 below. Dark plumes 

are expressed as numbers 1 through 5 on the Ringelmann chart, while light plumes are 

expressed as equivalent percentages. Thus, Ringelmann 1 corresponds to 20% opacity, 

Ringelmann 2 corresponds to 40% opacity, Ringelmann 3 to 60% opacity, Ringelmann 

4 to 80% opacity, and Ringelmann 5 corresponds to 100% opacity. 
MONTEREY BAY UNIFIED AIR POLLUTION CONTROL DISTRICT 

REGULATION IV 

PROHIBITIONS

5 

8/15/12 Rule 400 (Visible Emissions) 

2.4 Ringelmann Chart 

The chart used to designate shades of darkness of emissions as published by the United 

States Bureau of Mines. 

2.5 Startup 

The period of time when the equipment goes from a non-operational to a fully 

operational state. 

Good engineering practices shall be used to the fullest extent practicable during startup 

to minimize pollutant emissions. 

2.6 Teepee Burner 

A conical shaped device used to burn flammable forestry and agricultural product waste 

material in an enclosed fixture effective in preventing the spread of sparks or fire, 

situated in an area cleared of grass, grain, brush, slash, litter, and snags for a distance of 

100 feet surrounding the device or by landfill or other methods which meet applicable 

state and local fire safety, air, and water quality standards. A burn permit pursuant to 

Rule 438 must be obtained for use of such device. 

PART 3 REQUIREMENTS AND STANDARDS 

3.1 General Visible Emission Limitations 

A person shall not discharge into the atmosphere from any emission source whatsoever 

any air contaminant for a period or periods aggregating more than three minutes in any 

one hour, which is as observed using the appropriate test method referenced in Section 

4.1: 

3.1.1 as dark or darker in shade as that designated as No. 1 on the Ringelmann 

Chart, as published by the United States Bureau of Mines; or 

3.1.2 of such opacity as to obscure an observer's view to a degree equal to or greater 

than does smoke described in Subsection 3.1.1 above. 
MONTEREY BAY UNIFIED AIR POLLUTION CONTROL DISTRICT 

REGULATION IV 

PROHIBITIONS

6 

8/15/12 Rule 400 (Visible Emissions) 

3.2 Industry-Specific Visible Emission Limitations 

3.2.1 Abrasive Blasting 

Notwithstanding the requirements of Subsection 3.1 above, abrasive 

blasting operations shall not exceed visible emissions limits set by Sections 

92000 et seq. of Title 17 of the California Code of Regulations, which are 

20% opacity (or equivalent Ringelmann 1) for indoor operations using noncertified abrasive blasting material and 40% opacity (or equivalent 

Ringelmann 2) for more than 3 minutes in any hour for outdoor operations 

using the following methods: wet abrasive blasting, hydroblasting, vacuum 

blasting, or abrasives certified for permissible dry outdoor blasting. 

3.2.2 Drinking Water Systems 

Notwithstanding the requirements of Section 3.1, emissions of visible 

smoke from any diesel auxiliary engine or generator used exclusively to 

operate a drinking water system shall not exceed Ringelmann 2 (or 

equivalent 40% opacity), when operated under emergency circumstances, or 

operated not more than 30 minutes each week, or two hours each month, 

under non-emergency circumstances. {HSC Section 41701.6} 

3.2.3 Gas Turbines 

Notwithstanding the requirements of Section 3.1, visible emissions from 

gas-fired combustion turbines during startup may exceed Ringelmann 1 (or 

equivalent 20% opacity) for a period of not more than two hours, provided 

that visible emissions during such startup periods shall not exceed 

Ringelmann 2 (or equivalent 40% opacity) for a period or periods 

aggregating more than three minutes in any one hour. 

3.2.4 Pile Drivers 

Notwithstanding the requirements of Section 3.1, pile driver operations 

shall not exceed the visible emission limits set by Health and Safety Code 

Sections 41701.5, which are Ringelmann 1 (or equivalent 20% opacity) for 

no more than 4 minutes per pile, or Ringelmann 2 (or equivalent 40% 

opacity) for no more than 4 minutes per pile if operating on kerosene, 

smoke suppressing additives and synthetic lubricating oil. 

3.2.5 Federally Regulated Industries 

In addition to the general visible emission limits of Section 3.1 above, 
MONTEREY BAY UNIFIED AIR POLLUTION CONTROL DISTRICT 

REGULATION IV 

PROHIBITIONS

7 

8/15/12 Rule 400 (Visible Emissions) 

industries subject to any visible emission limit codified in 40 CFR Part 60, 

40 CFR Part 61, or 40 CFR Part 63 shall comply with those limits. For 

reference, District Rules 423 (New Source Performance Standards) and 424 

(National Emission Standards for Hazardous Air Pollutants) include lists of 

the industry-specific standards which have been promulgated in 40 CFR 

Parts 60 and 61 respectively. 

PART 4 ADMINISTRATIVE REQUIREMENTS 

4.1 Test Methods 

4.1.1 Except for any visible emission limits codified in 40 CFR Part 60, 40 CFR Part 

61, or 40 CFR Part 63, all visible emissions determinations shall be in accordance 

with EPA Method 9 (Visual Determination of the Opacity of Emissions from 

Stationary Sources) except for the data reduction procedures. Data reduction 

shall consist of counting the number of observations above the applicable 

standard and multiplying that number by 0.25 to determine the minutes of 

emissions above an applicable standard. 

4.1.2 Visible emissions for any visible emission limit codified in 40 CFR Part 60, 40 

CFR Part 61, or 40 CFR Part 63 shall be observed in accordance with the 

observation procedure contained within EPA Method 9 or Method 22 (Visual 

Determination of Fugitive Emissions from Material Sources and Smoke 

Emissions from Flares), as applicable, codified as Appendix A of 40 CFR Part 60. 

 * * * * *