• What is the American Conference of Governmental Industrial Hygienists (ACGIH) recommended exposure limit for phosphoric acid?
• What are the fire and explosion dangers associated with phosphoric acid?
• Is phosphoric acid stable when exposed to air, moisture, or heat?
• Are there any conditions to avoid when using phosphoric acid?
• Does phosphoric acid have an odour threshold (at what level can I smell it)?
• Is the odour of phosphoric acid reliable as a warning property?
• How can I work with phosphoric acid safely?
• What can be done to control hazardous conditions?

What is the American Conference of Governmental Industrial Hygienists (ACGIH) recommended exposure limit for phosphoric acid?

TIME-WEIGHTED AVERAGE (TLV-TWA): 1 mg/m³

STEL: 3 mg/m³

TLV BASIS - CRITICAL EFFECT(S) : Irritation

NOTE: In many Canadian jurisdictions, exposure limits are similar to the ACGIH TLVs. Since the manner in which exposure limits are established, interpreted, and implemented can vary, obtain detailed information from the appropriate government agency in each jurisdiction.

What are the fire and explosion dangers associated with phosphoric acid?

Phosphoric acid does not burn. It can react with most metals to produce highly flammable hydrogen gas that may explode if ignited. During a fire, irritating/toxic phosphorus oxides may be generated. Containers may explode in the heat of a fire.

Is phosphoric acid stable when exposed to air, moisture, or heat?

Normally stable. Orthophosphoric acid gradually changes to pyrophosphoric acid at about 200 deg C and forms metaphosphoric acid above 300 deg C.

Are there any conditions to avoid when using phosphoric acid?

Heat

Does phosphoric acid have an odour threshold (at what level can I smell it)?

Not applicable. Phosphoric acid is odourless.

Is the odour of phosphoric acid reliable as a warning property?

POOR - No odour warning properties.

How can I work with phosphoric acid safely?

This material is CORROSIVE. Before handling it is very important that engineering controls are operating and that protective equipment requirements and personal hygiene measures are being followed. People working with this chemical should be properly trained regarding its hazards and its safe use. Immediately report leaks, spills or failures of the engineering controls.

Avoid generating mists. Prevent the release of vapours or mists into the air. Unprotected persons should avoid all contact with this chemical including contaminated equipment. Always inspect containers for damage or leaks before handling them. Cautiously dispense into sturdy containers made of compatible materials. Use the type of container recommended by the manufacturer. Use corrosion-resistant transfer when dispensing. Whenever possible, use self- closing, portable containers for dispensing small amounts of this material. Never transfer liquid by pressurizing original container with air or inert gas. Use smallest possible amounts in designated areas with adequate ventilation. Have emergency equipment (for fires, spills, leaks, etc.) readily available.

Do not use with incompatible materials such as strong caustics. Corrosion of equipment and surfaces should be considered in areas where hot or misted phosphoric acid is present. Soda ash or lime should be kept nearby for emergency use.

Label containers. Keep containers closed when not in use. Empty containers may contain residues that are hazardous. Never return contaminated material to its original container. Immediately contact the chemical manufacturer/supplier for handling instructions if drums of this material appear to be swollen. Follow chemical manufacturer's/supplier's advice regarding venting of drums.

When preparing or diluting acid solutions, the acid should be added slowly to water with plenty of careful stirring. This will prevent overheating, splashing and splattering of the acid.

Follow handling precautions on Material Safety Data Sheet. Practice good housekeeping. Maintain handling equipment. Comply with applicable regulations.

What can be done to control hazardous conditions?

Engineering control methods to reduce hazardous exposures are preferred. Methods include mechanical ventilation (dilution and local exhaust), process or personnel enclosure, control of process conditions, and process modification (e.g., substitution of a less hazardous material). Administrative controls and personal protective equipment may also be required.

Local exhaust ventilation and enclosure may be necessary when this material is heated or a mist created. Use a corrosion-resistant ventilation system separate from other ventilation systems. Exhaust directly to the outside. Supply sufficient replacement air to make up for air removed by exhaust systems.

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Document confirmed current on January 15, 2003

Document last updated on February 19, 1999

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