Industrial hygiene in Yuma: where the field ends and the plant begins

Yuma is one of the country's main regions for growing and packing winter vegetables. It is also where the line between agricultural rules and general industry standards really matters, because the same head of lettuce crosses it.

Our field is industrial hygiene, the discipline behind workplace air monitoring and noise surveys.

The line that runs through a packing shed

In the field, most of the rules are not OSHA's. Pesticide handling, and when workers may go back into a treated field, fall under the Worker Protection Standard. That is an EPA rule, and in Arizona it is enforced by the state pesticide program, not by workplace safety inspectors.

OSHA's part in crop production is narrow, and its field sanitation standard is the best-known piece. In addition, limits written into the annual federal appropriations bills have long barred OSHA enforcement at farms with 10 or fewer employees and no temporary labor camp.

Step into the cooler, the packing shed or the processing plant, and you are in general industry, where OSHA's full set of general industry standards applies. That includes the standards on:

• Exposure monitoring
• Hearing conservation programs
• Respiratory protection
• Confined spaces
• Hazard communication
• Lockout/tagout

Our part of that list is the air monitoring and the noise surveys.

Companies that run both sides often manage all of it by the agricultural rules, because that is where the business started. The processing side is where the OSHA citations are.

Ammonia, and what packing houses really run

Cooling and cold storage at this scale means industrial ammonia refrigeration. Anhydrous ammonia comes under OSHA's Process Safety Management standard at 10,000 pounds. The calculation covers the whole process, and vessels that are connected count as one process. You therefore add together the receiver, accumulators, surge drums, coils and the ammonia in the piping. EPA's Risk Management Program has the same threshold under a separate rule.

The exposure limits for ammonia are:

• OSHA permissible exposure limit (PEL): 50 parts per million (ppm)
• ACGIH threshold limit value (TLV) and NIOSH recommended exposure limit (REL): 25 ppm as a time-weighted average (TWA), and 35 ppm as a short-term exposure limit (STEL)
• The level that is immediately dangerous to life or health: 300 ppm

Vacuum cooling deserves separate mention. Vacuum tube coolers pull leafy greens down to a near-vacuum, which chills them by evaporation. The hazard is the vessel itself, not an airborne concentration. It is a confined space with a mechanical hazard and an entry procedure.

Then comes the wash line:

• Chlorine has an OSHA ceiling limit of 1 ppm, a level that must not be exceeded at any time. It is not a time-weighted average.
• Peracetic acid has no OSHA PEL at all. ACGIH's TLV is a 15-minute STEL of 0.4 ppm. Peracetic acid is genuinely difficult to sample well, because it exists in equilibrium with hydrogen peroxide and acetic acid. An analytical method that picks out only acetic acid gives a reassuring number that says nothing about the peracetic acid.

Last is carbon monoxide from propane forklifts in sealed cold rooms, which is overlooked again and again in refrigerated handling.

→ Ammonia air monitoring · Carbon monoxide monitoring · Food and beverage plants

Heat is a hazard with no standard of its own

Yuma makes heat impossible to ignore, so it is worth being exact about the law.

There is no federal OSHA heat standard. Federal enforcement runs through the General Duty Clause, the law's general duty to keep a workplace free of known serious hazards. A federal standard on preventing heat injury and illness is still in rulemaking. OSHA's National Emphasis Program on heat expired on April 8, 2026 and has not been renewed, so it is not part of enforcement today.

Arizona has no heat standard either. Arizona is an OSHA State Plan state, which means it runs its own workplace safety program. Enforcement is through ADOSH, the state agency that administers the plan, under the Industrial Commission of Arizona. The state adopts the federal standards, but having no standard is not the same as having no enforcement. Two Arizona-specific measures now exist:

• The Industrial Commission of Arizona adopted workplace heat safety guidelines on April 9, 2026.
• ADOSH runs an Arizona Heat State Emphasis Program, revised April 9, 2026, which directs inspections and outreach at heat exposure.

Neither one is an enforceable standard. What they do is set out what ADOSH expects to see when it arrives, and a General Duty Clause case gets built from that same material.

In practice there is no number to meet, so your defense is the quality of your heat program. Acclimatization, which means getting workers used to the heat, carries the most weight. A large majority of heat deaths happen in a worker's first days on the job, which means new hires, returning seasonal crews and anyone back from a long break.

Heat also makes everything else on this page worse. In the same conditions, workers tolerate respirators less, wear PPE less consistently and report their own symptoms less accurately.

→ Respirators and air monitoring

Military aviation support

Marine Corps Air Station Yuma and Yuma Proving Ground anchor a large base of defense maintenance and test-support work. Aviation maintenance has its own set of hazards, and the choice of sampling filter for each one leaves no room for error.

• Hexavalent chromium, from chromate conversion coatings and primers. OSHA's PEL is 5 micrograms per cubic meter of air (µg/m³), and the action level is 2.5 µg/m³.
• Isocyanates, from polyurethane topcoats
• Solvents and JP-8 jet fuel in fuel systems work
• High-level noise from engine runs and ground equipment runs

Hexavalent chromium requires one filter type for plating and another for painting and welding, and isocyanates require a specially treated filter, known as a derivatizing filter. With the wrong one, a dirty hangar gets a clean number.

→ Hexavalent chromium air sampling · Isocyanate air sampling · Noise surveys

Practical notes

Yuma County does not run its own air program. Only Maricopa, Pima and Pinal counties do. Air permits therefore come from ADEQ, the Arizona Department of Environmental Quality, which is unlike the Phoenix and Tucson answers.

Yuma also does not meet a federal air quality standard for particulate matter. The official term is a PM10 nonattainment area. ADEQ lists Yuma, in Yuma County, as nonattainment for PM10 against the 1987 National Ambient Air Quality Standard (NAAQS).

In farming and earthmoving country, the dust control requirements reach unpaved yards, haul routes, stockpiles, land preparation and construction. They apply on top of normal permits, not in place of them. It is the kind of requirement that gets discovered during construction when it should have been identified beforehand.

Process safety work, heat stress surveys, heat programs, air permits and dust rules are outside the four fields we work in. We name them here so you know they apply.

We work from one Arizona office, with no Yuma branch. Yuma is roughly 3 hours away on I-8, so we plan Yuma projects to finish in consecutive days and not in repeat trips. We also calibrate our equipment on your site, not before we leave.

We work in four fields here:

• Tier II chemical inventory reporting (due March 1)
• Form R / TRI reporting (due July 1)
• Air monitoring surveys and noise surveys
• ISO consulting for environmental management (ISO 14001) and for occupational health and safety (ISO 45001)

→ Where we work