Food and beverage plants: ammonia, dust, CO₂ and line noise

Food and beverage plants have their own set of airborne hazards, chiefly ammonia, grain and flour dust, carbon dioxide, sanitizers and carbon monoxide. Filling and packaging lines add noise.

Airborne ammonia

OSHA's permissible exposure limit (PEL) for ammonia is 50 parts per million (ppm) as a time-weighted average (TWA) over the shift. ACGIH and NIOSH both recommend a lower figure: 25 ppm as a TWA, with a 35 ppm short-term exposure limit (STEL). The level that is immediately dangerous to life or health is 300 ppm.

A fixed ammonia detection system in an engine room is a life-safety and leak-detection tool, not an exposure record for the operator who spent 40 minutes on a coil.

→ How we monitor for ammonia

Ammonia refrigeration: the inventory counting mistake

This topic is outside the four fields we work in, but we include it because we see the same error again and again.

OSHA's Process Safety Management standard applies to facilities with large quantities of highly hazardous chemicals, and it covers anhydrous ammonia at a threshold of 10,000 pounds.

The error is counting only the largest vessel. The high-pressure receiver holds 6,000 pounds, so the plant concludes that the standard does not apply.

The standard applies to a process, and a process includes any group of vessels that are interconnected. It also includes separate vessels close enough that a release from one could involve the other. The receiver, accumulators, intercooler, surge drums, evaporator coils and the ammonia in the piping are one process if they are connected. Very few industrial systems in a distribution-scale cold storage building are under 10,000 pounds once the inventory is added up honestly.

Cross that threshold and the list of requirements is long:

• Process safety information
• A process hazard analysis
• Written operating procedures
• Mechanical integrity
• Management of change
• Compliance audits every 3 years
• The rest of the standard

EPA has a Risk Management Program at the same 10,000-pound threshold, which is a separate rule with a separate filing.

Grain dust and flour dust are two different problems

Grain dust has its own entry in OSHA's table of air contaminant limits: 10 milligrams per cubic meter of air (mg/m³) as an 8-hour TWA. Flour dust is not in that table at all. ACGIH's threshold limit value (TLV) for flour is 0.5 mg/m³, measured as inhalable dust, which is 20 times lower. It is set to prevent sensitization (the body developing a reaction to a substance), not to control nuisance dust.

Baker's asthma is driven by allergens in wheat protein and also by fungal alpha-amylase, an enzyme added to improve dough, which is a strong sensitizer in its own right. A mixing room can pass a grain dust comparison with room to spare and still be a place where workers become sensitized.

Then there is the dust explosion hazard. OSHA's grain handling standard covers grain handling facilities and includes housekeeping requirements, and a fire safety standard called NFPA 61 covers agricultural and food processing. OSHA has no general standard for combustible dust. Outside the grain handling standard, it enforces through its combustible dust emphasis program and the General Duty Clause.

→ How we monitor airborne dust

Carbon dioxide in fermentation and beverage plants

Carbon dioxide (CO₂) is heavier than air and collects in the low points, including cellar floors, tank pits, stairwells to a fermentation room and the inside of any vessel that has held beer or wine.

• OSHA PEL: 5,000 ppm
• ACGIH TLV: 5,000 ppm as a TWA, with a 30,000 ppm STEL
• Immediately dangerous to life or health: 40,000 ppm

The margin between the occupational limit and immediate danger is narrower than people assume. Unlike the atmosphere in most confined spaces, the hazard is not only that CO₂ displaces oxygen, because CO₂ is directly toxic at concentrations well below the point of oxygen deficiency.

Any tank entry, cellar or CO₂-blanketed vessel in a brewery, winery or beverage plant falls under OSHA's confined space standard, so it is a confined space question before it is an air monitoring question.

Sanitizers, which are difficult to sample well

Peracetic acid (PAA) has no OSHA PEL. ACGIH sets a 15-minute STEL of 0.4 ppm and nothing else. Sampling it well is genuinely difficult, because PAA exists in equilibrium with hydrogen peroxide and acetic acid. A method that isolates only acetic acid gives a number that looks reassuring and tells you nothing about the PAA.

Chlorine has a 1 ppm OSHA ceiling limit, a level that must not be exceeded at any time, and it is not a TWA. ACGIH's TLV is 0.1 ppm, with a 0.4 ppm STEL. Exposures occur when clean-in-place (CIP) solutions are mixed, when foam is applied, and at the moment a sanitizer meets an incompatible cleaner.

Two hazards that get overlooked

Carbon monoxide (CO) in cold storage. Propane forklifts, sealed rooms, doors kept shut to hold temperature and engines that run rich when cold make this one of the most often overlooked CO settings in industry. The OSHA PEL is 50 ppm, and the ACGIH TLV is 25 ppm.

Noise on filling and packaging lines. Can and bottle handling produces sharp impact noise with very high peaks. A single overall decibel reading (dBA) tells you the level but nothing about the fix. Octave band analysis, which breaks the noise down by frequency from low to high, usually points to a guide rail, an air nozzle or a transfer point, not to a wall.

→ Carbon monoxide monitoring · Noise surveys

What we do for food and beverage plants

An air monitoring survey measures what your workers are breathing, and a noise survey measures the noise exposure of each job. We also help with ISO 14001, the international standard for environmental management systems. Combustible dust and confined space programs are outside the four fields we work in.