OAR 437-004-9000
Oregon Rules for Air Contaminants


An employee’s exposure to any substance in Oregon Tables Z-1, Z-2, or Z-3 of this section must be limited in accordance with the requirements of the following paragraphs of this section.

(1)

Oregon Table Z-1.

(a)

Substances with limits preceded by “C” – ceiling values. An employee’s exposure to any substance in Oregon Table Z-1, the exposure limit of which is not preceded by a “C”, must at no time exceed the ceiling exposure limit given for that substance. If instantaneous monitoring is not feasible, then assess the ceiling as a 15-minute time-weighted average. This exposure level must never be exceeded at any time during the workday.

(b)

Other substances — 8-hour time-weighted averages (PEL-TWA). An employee’s exposure to any substance in Oregon Table Z-1, the exposure limit of which is not preceded by a “C”, must not exceed the 8-hour Time-Weighted Average for that substance in any 8-hour shift of a 40-hour work week.

(c)

Other substances — Excursion Limits. Excursions in exposure levels may be more than three times the PEL-TWA number for no more than a total of 30 minutes during a workday, and must never be more than five times the PEL-TWA, provided that the overall 8-hour PEL-TWA is not exceeded.

(d)

Skin designation. To prevent or reduce skin absorption, you must prevent or reduce an employee’s skin exposure to substances listed in Oregon Table Z-1 with an “X” in the Skin designation column following the substance name. Prevent or reduce exposure to the extent necessary in the cirumstances through the use of gloves, coveralls, goggles, or other appropriate personal protective equipment, engineering controls or work practices.

(e)

Oregon Table Z-1 in Division 4/Z, OAR 437-004-9000 (Oregon Rules for Air Contaminants), has a complete list of regulated substances. If your operation exposes an employee to a substances listed in Oregon Table Z-1, and that substance includes a reference to another rule, that rule may apply to your circumstances.

(2)

Oregon Table Z-2. An employee’s exposure to any substance listed in Oregon Table Z-2 must not exceed the following exposure limits:

(a)

8-hour time-weighted averages. An employee’s exposure to any substance in Oregon Table Z-2, in any 8 hour work shift of a 40-hour work week, must not exceed the 8-hour time-weighted average limit for that substance in Oregon Table Z-2.

(b)

Acceptable ceiling concentrations. An employee’s exposure to a substance in Oregon Table Z-2 must not exceed the acceptable ceiling concentration for that substance during an 8-hour shift except:
(i)
Acceptable maximum peak above the acceptable ceiling concentration for an 8-hour shift. An employee’s exposure to a substance in Oregon Table Z-2 must never exceed the acceptable maximum peak above the acceptable ceiling concentration and must not exceed the maximum duration of exposure at that level for the substance during an 8-hour shift.

(c)

Example. During an 8-hour work shift, an employee’s exposure to benzene is limited to an 8-hour time-weighted average (TWA) of 10 ppm. The acceptable ceiling concentration of benzene during the 8-hour work shift is a maximum of 25 ppm, unless that exposure is no more than 50 ppm and for not longer than 10 minutes during an 8-hour work shift. Such exposures must be compensated by lower exposure levels (concentrations below the TWA number – 10 ppm) during that shift so that the overall 8 hour time-weighted average is a maximum of 10 ppm. Example Table.

(d)

Skin designation. To prevent or reduce skin absorption, you must prevent or reduce an employee’s skin exposure to substances listed in Oregon Table Z-2 with an “X” in the Skin designation column following the substance name. Prevent or reduce exposure to the extent necessary in the circumstances through the use of gloves, coveralls, goggles, or other appropriate personal protective equipment, engineering controls, or work practices.

(3)

Oregon Table Z-3. An employee’s exposure to any substance in Oregon Table Z-3, in any 8-hour work shift of a 40-hour work week, must not exceed the 8-hour time-weighted average limit given for that substance.

(4)

Computation formulae. The computation formulae that apply to exposures to one or more substances, with 8-hour time-weighted averages included in OAR 437, Division 4/Z, Chemicals/Toxins, in order to determine whether an employee is exposed is over the regulatory limit are as follow:

(a)

For a single air contaminant:
(i)
Compute the cumulative exposure for an 8-hour work shift as follows:
E = (CaTa + CbTb + ...CnTn) ÷ 8
Where:
E is the equivalent exposure to that substance for the shift.
C is the concentration during any period T where the concentration remains constant.
T is the duration in hours of the exposure at the concentration C.
The value of E must not exceed the 8-hour time-weighted average specified for that substance in Subdivision 4/Z.
(ii)
To illustrate the formula in (4)(a)(i) above, assume that Substance A (from Oregon Table Z-1) has an 8 hour time-weighted average limit of 100 ppm. Assume that an employee is subject to the following exposure:
Two hours exposure at 150 ppm
Two hours exposure at 75 ppm
Four hours exposure at 50 ppm
Substituting this information in the formula, we have:
[(Ca x Ta) + (Cb x Tb) + ... (Cn x Tn)] ÷ 8 = E =TWA
[(2 x 150) + (2 x 75) + (4 x 50)] ÷ 8 = 81.25 ppm
Since 81.25 ppm is less than 100 ppm, the 8-hour time-weighted average limit, the exposure is acceptable.

(b)

For a mixture of air contaminants:
(i)
In case of a mixture of air contaminants, compute the equivalent exposure as follows:
Em = (C1 ÷ L1) + (C2 ÷ L2) + . . .(Cn ÷ Ln)
Where:
Em is the equivalent exposure for the mixture.
Cn is the concentration of a particular contaminant.
Ln is the exposure limit for that substance in Subdivision 4/Z.
The value of Em must not exceed “unity” (1).
(ii)
To illustrate the formula in (4)(b)(i) above, consider the following exposures:
Table.
Substituting in the formula, we have:
Em = (C1 ÷ L1) + (C2 ÷ L2) + . . .(Cn ÷ Ln)
Em = (500 ÷ 1000) + (45 ÷ 200) + (40 ÷ 200)
Em = 0.500 + 0.225 + 0.200
Em = 0.925
Since Em (0.925) is less than unity (1), the exposure combination is within acceptable limits.

(5)

Engineering or administrative controls. To achieve compliance with the exposure limits in paragraphs (1) through (4) of this section, first determine and implement, when feasible, engineering or administrative controls. When such controls are not feasible, mandate the use of protective equipment or any other protective measures to keep exposure within the limits in this section. Any equipment or technical measures used for this purpose must be approved for each particular use by a competent Industrial Hygienist or other technically qualified person. Whenever using respirators, comply with Division 4/I, OAR 437-004-1040, Respiratory Protection. Tables Z-1, Z-2, Z-3, and notes.
[ED. NOTE: Tables and Notes referenced are available from the agency.]
[ED. NOTE: To view attachments referenced in rule text, click here to view rule.]

Source: Rule 437-004-9000 — Oregon Rules for Air Contaminants, https://secure.­sos.­state.­or.­us/oard/view.­action?ruleNumber=437-004-9000.

437–004–0001
Application
437–004–0002
Scope
437–004–0003
Exclusive Coverage
437–004–0005
Access to Employee Exposure and Medical Records
437–004–0099
General Standards
437–004–0100
Universal Definitions
437–004–0150
Standards Organizations
437–004–0240
Safety Orientation for Seasonal Workers
437–004–0251
Safety Committees and Safety Meetings
437–004–0310
Working Surfaces
437–004–0320
Guarding Floor and Wall Openings and Holes
437–004–0330
Fixed Industrial Stairs
437–004–0340
Portable Ladders
437–004–0350
Orchard Ladders
437–004–0360
Fixed Ladders
437–004–0370
Scaffolding
437–004–0380
Manually Propelled Mobile Ladder Stands and Scaffolds (Towers)
437–004–0390
Other Working Surfaces
437–004–0405
Exits and Emergency Action Plan
437–004–0450
Emergency Action Plan
437–004–0570
Manlifts
437–004–0610
Ventilation
437–004–0630
Noise Exposure
437–004–0650
Ionizing Radiation
437–004–0710
Compressed Gases
437–004–0715
Acetylene
437–004–0716
Oxygen
437–004–0717
Hydrogen
437–004–0720
Flammable and Combustible Liquids
437–004–0725
Spray Finishing
437–004–0770
Explosives and Blasting Agents
437–004–0780
Storage and Handling of Liquefied Petroleum Gases
437–004–0790
Use of Liquefied Petroleum Gas or Natural Gas in Fields and Orchards
437–004–0800
Storage and Handling of Anhydrous Ammonia
437–004–0950
Hazardous Waste Operations and Emergency Response (HAZWOPER)
437–004–1005
General Requirements for Protective Equipment
437–004–1020
Personal Fall Protection
437–004–1030
Work Clothing
437–004–1035
Eye and Face Protection
437–004–1041
Respiratory Protection
437–004–1050
Head Protection
437–004–1060
Hand, Foot, and Extremity Protection
437–004–1070
Working Underway on Water
437–004–1075
Working Over or In Water
437–004–1105
Sanitation
437–004–1110
Field Sanitation for Hand Labor Work
437–004–1115
COVID-19 Workplace Requirements for Employer-Provided Labor Housing
437–004–1120
Agricultural Labor Housing and Related Facilities
437–004–1140
Lighting
437–004–1150
Safety Colors for Marking Physical Hazards
437–004–1180
Accident Prevention Signs
437–004–1250
Confined and Hazardous Spaces
437–004–1260
Manure Lagoons, Storage Ponds, Vats, Pits and Separators
437–004–1275
The Control of Hazardous Energy (Lockout/Tagout)
437–004–1305
Medical Services and First Aid
437–004–1430
Sources of Fire
437–004–1440
Required Postings
437–004–1450
Extinguishers
437–004–1460
Fire Prevention Plan
437–004–1470
Employee Equipment and Training
437–004–1505
Air Receivers and Pressure Systems
437–004–1525
Boilers and Steam Systems
437–004–1610
General Requirements
437–004–1630
Conveyors
437–004–1670
Automotive Hoists
437–004–1680
Storage of Hazardous Chemicals
437–004–1700
Forklifts and Other Powered Industrial Trucks
437–004–1750
Helicopters
437–004–1805
Rope, Chain, Rigging, and Hoists
437–004–1825
Tackle and Hoisting Equipment
437–004–1910
General Equipment Guarding
437–004–1940
Farm Field Equipment
437–004–1970
Farmstead Equipment
437–004–2000
Powered Saws
437–004–2100
Grinders
437–004–2220
General Requirements — Small Tools
437–004–2230
Guarding and Operation of Portable Powered Tools
437–004–2240
Power Lawnmowers
437–004–2260
Other Portable Tools and Equipment
437–004–2310
General Requirements
437–004–2350
Oxygen-Fuel Gas Welding and Cutting
437–004–2400
Arc Welding and Cutting
437–004–2810
General Requirements
437–004–2850
Temporary Lighting and Wiring
437–004–2860
Flexible Cable and Extension Cords
437–004–2870
Attachment Plugs and Receptacles
437–004–2880
Cord and Plug-Connected Equipment
437–004–2900
Grounding and Bonding
437–004–2950
Switches and Circuit Breakers
437–004–3000
Identification and Load Ratings
437–004–3050
Work Near Overhead Lines
437–004–3075
Agricultural Buildings with Special Hazards
437–004–3100
Excavation
437–004–3410
Agricultural, Commercial and Industrial Vehicles
437–004–3420
Working from Vehicles and Vehicle Loads
437–004–3430
Training for Agriculture Tractor Operators
437–004–3460
Industrial Vehicles
437–004–3480
Bridges, Roads and Ramps
437–004–3550
Servicing Multi Piece and Single Piece Rim Wheels
437–004–3600
Roll-Over Protective Structures (ROPS) for Tractors in Agriculture
437–004–3650
Roll-Over Protective Structures — Industrial Vehicles
437–004–3660
Vehicle-Mounted Elevating and Rotating Work Platforms
437–004–6000
Adoption by Reference of Federal Standard
437–004–6001
Expiration and Implementation Dates
437–004–6401
Effective dates for worker training programs in Oregon
437–004–6405
Restrictions Associated With Outdoor Production Pesticide Applications
437–004–6406
Pesticide Spray Drift and Innovative Methods
437–004–6501
Handler training programs in Oregon
437–004–6502
Oregon requirements for Worker Protection Standard trainers of handlers who qualify using train-the-trainer programs
437–004–6508
Respiratory Protection
437–004–6509
Emergency eye-washes and eye flushing supplies
437–004–9000
Oregon Rules for Air Contaminants
437–004–9010
Fumigated Areas.
437–004–9050
Asbestos
437–004–9090
13 Carcinogens
437–004–9600
Lead
437–004–9620
Cadmium
437–004–9626
Chromium (VI)
437–004–9640
Benzene
437–004–9650
Bloodborne Pathogens
437–004–9710
Acrylonitrile
437–004–9720
Thiram
437–004–9740
Ethylene Oxide
437–004–9760
Formaldehyde
437–004–9780
Methylendianiline
437–004–9800
Hazard Communication Standard for Agricultural Employers
437–004–9830
Retention of Department of Transportation (DOT) Markings, Placards and Labels
437–004–9850
Pipe Labelling
437–004–9860
Hazardous Chemicals in Laboratories
Last Updated

Jun. 8, 2021

Rule 437-004-9000’s source at or​.us