Hydrofluoric Acid

The following is the manual used to train cleanroom personnel about handling and storing Hydrofluoric acid:

Description of HF

Physical Properties of HF:
Vapor has an acrid, irritating odor
Colorless, clear, fuming liquid
Miscible with water
Vapor pressure = 14 mmHG at 20 C
Hydrofluoric acid (HF) is a weak acid as defined in chemestry - only partly ionizes in water.

Prior to Performing Work

Make sure all containers are labeled properly - remember HF is a clear liquid and can be mistaken for water. In addition to labeling containers, the laboratory needs to designate and assign a location for use of HF.

Skin Exposure and Hazards

Initial Signs of Exposure:

Redness
Blistering
Edema, an Abnormal excess accumulation of serous fluid in connective tissue or in a body caviy

Advanced Signs of Exposure:

Painful deep seated burns that are slow to heal.
HF BURNS POSE UNIQUE DANGERS DISTINCT FROM OTHER INORGANIC ACIDS SUCH AS HCL AND SULFURIC ACID. SOME DIFFERENCES INCLUDE:
The fluoride ion readily penetrates the skin
Deep tissue is damaged
Note: If left untreated damage may continue for days
De-mineralization of the body occurs
DIFFERENT THAN OTHER INORGANIC ACIDS
Readily penetrates the skin and the onset of pain may be delayed.

Skin/Eye Exposure

Severity of Skin Exposure is Dependent Upon at Least:
Concentration
Surface Area Exposed
Duration fo Contact
Temperature
Note: All exposures require immediate first aid and medical attention

How Toxic is Hydrofluoric Acid?

Toxicity Comparison:

Carbon Monoxide: LC50=1807ppm, 4 hours
Hydrogen Fluoride: LC50=342ppm, 60 minutes
Arsine, Arsenic Hydride: LC50=94ppm, 15 minutes
Hydrogen Cyanide: LC50=63ppm, 40 minutes

HF Vapor, Airborne Exposure Limits

OSHA (based upon outdated information): Permissible Exposure Limit = 3ppm
Note: An airborne permissible exposure limit (PEL) is the 8-hour tmie weighted average not to be exceeded.

ACGIH 2006 (based upon recent health data):

Threshold Limit Value TWA = .5 ppm
Threshold Limit Value Ceiling Limit = 2 ppm
Note: A TWA is the 8-hour time weighted average not to be exceeded. A ceiling limit is the airborne concentration that should never be exceeded.
AIRBORNE HF IS ESPECIALLY DANGEROUS BECAUSE:
· You can't rely upon sight to detect it's presence
· The airborne limits are very close to the odor threshold (Odor Threshold: Less than 1 ppm)
· Inhalation may cause pulmonary edema
EXPOSURE TO AIRBORN HF
It is impossible to distinguish between 1 & 2 ppm using your sense of smell
When working with HF you should not be able to smell it.
If you can smell HF (acrid, irritating odor) when working with it, stop work and speak with the lab manager. The controls being used may be inadequate or may have stopped functioning properly.

Summary of Exposure

Exposure Routes
Eye/Skin Absorption
Inhalation and Ingestion
Individuals can be exposed to HF through any route of exposure. Reference your lab safety procedures to find out what controls to use, how to use them, and when.

Exposure Control Heirarchy

Most Preferred: Engineering Controls
Less Preferred: Administrative Controls
Least Preferred: Personal Protective Equipment
In most situations it is necessary to us engineering controls in conjunction with other controls. OSHA requires implementation of engineering controls (if practical and feasible) prior to using the other controls.

Exposure Controls

The best treatment for exposure is prevention. Use a less toxic/dangerous chemical if possible. Controls that are used to control HF exposure must be designed for such use, and used in accordance with manufacturer recommendations.
Some of the controls you may need to use include:
  1. Acid Digestion Hood with Polycarb Sash and Plastic Ducting
  2. Splash Goggles
  3. Gloves
  4. Face Shield
  5. Acid Smock 
Reference your lab safety procedures to find out what controls to use, how to use them, and when.

Buddy System

Never work alone when using HF. The extra person does not use HF, instead they are to summon emergency services, direct the victim, and prevent further damage.

Role of the Buddy in the Event of Exposure

Verbally direct the victim to use the emergency shower for a maximum of five minutes, and then to immediately apply calcium gluconate to the exposed skin.
Immediately call 911 to summon emergency services.
Note: Do not remain in an area of the lab where exposure may continue.
Provide Material Safety Data Sheet (MSDS) and Calcium Gluconate to the emergency responders.
Note: all the information needed is stored in an envelope next to the Calcium Gluconate.
Cordon off the lab, or contaminated area, to prevent others from being exposed and spreading contamination.
Contact the lab manager to find out how clean-up should proceed. Contact police if you are not prepared to clean-up HF.

The Victim Does the Following as Soon as Possible

· Use the emergency flushing facilities (eyewash/shower) for five minutes.
· Disrobe while using the flushing facilities. Not doing so will hold acid against the skin. Do not bother to dry off.
· Immediately apply Calcium Gluconate to all surface areas of the body that have been exposed to liquid HF. Use gloves.
· Note: If Calcium Gluconate is not available rinse for 15 minutes.
· Continue rubbing the calcium gluconate into the skin until redness or pain has disappeared.
· Note: Emergency may be transporting you to the hospital by this point.
· Be prepared to explain how you were exposed to HF (skin, inhalation, ingestion, injection), what concentration of HF was being used at the time of exposure, and what time the exposure occured.

Other First Aid Information for HF Exposure

· Eye Exposure - Rinse eyes out for 5 minutes.
· Inhalation - Relocate to fresh air.
· Ingestion - Drink two glasses of water the consume two glasses of milk or antacids.
· Always seek immediate medical attention following first aid.

HF Awareness Training Summary

· When possible avoid using HF.
· HF is extremely toxic and corrosive.
· HF can enter the body through any root of exposure.
· When using HF, you should not be able to smell it.
· Never work alone when using HF.
· Always use the exposure controls necessary to prevent exposure to HF (ventilation, etc.).
· If your skin/eyes are exposed to HF, immediately use the emergency shower/eyeflush for five minutes (15 if there is no Calcium Gluconate).
· Massage exposed area with Calcium Gluconate immediately after showering.
· Always seek immediate medical attention following first aid.