recommends that worker exposure to ammonia be controlled by requiring com pliance with the following sections. The standard is designed to protect the health and safety of workers for a 40-hour workweek over a working lifetime. Compliance with all sections of the standard should prevent adverse effects of exposure to ammonia in the workplace air. The standard is measurable by techniques that are valid, reproducible, and available to industry and government agencies. Sufficient technology exists to permit compliance with the recommended standard. The standard will be subject to review and revision as necessary. "Ammonia" is defined as gaseous or liquified anhydrous ammonia and aqueous solutions thereof (aqua ammonia, ammonium hydroxide). "Strong aqua ammonia" is defined as aqueous solutions containing more than 10% ammonia. "Weak aqua ammonia" is defined as solutions of 10% or less. Section 1 -Environmental (Workplace Air) (a) Concentration Occupational exposure shall be controlled so that no worker Is exposed to ammonia at greater than a celling concentration of 50 ppm as determined by a 5-minute sampling period. (b) Sampling and Analysis Procedures for sampling, calibration of equipment, and analysis of ammonia samples shall be as provided in Appendices I and II, or by any method shown to be equivalent in precision, accuracy, and sensitivity to the methods specified. I. RECOMMENDATIONS FOR AN AMMONIA STANDARD Section 2 -Medical (a) Preplacement medical examinations shall be made available for all workers whose employment may involve potential exposure to ammonia con centrations in excess of 50 ppm. The examination shall be directed toward, but not limited, to the eyes, skin, and upper respiratory system. Pulmonary function tests should be carried out at the time of the preplacement examination. An evaluation of the advisability of the worker's using negative or positive pressure respirators shall be made. (b) Medical surveillance shall be made available for all workers in whose eyes liquid ammonia has been splashed, who have signs and symptoms of eye irritation after exposure to ammonia, who exhibit signs or symptoms of respiratory tract (throat, trachea, lungs) irritation caused by ammonia exposure, or who experience skin irritation as a result of ammonia exposure. (c) Initial examinations for presently employed workers shall be made available within 6 months of the promulgation of a standard incorpor ating these recommendations. (d) Records of preplacement medical examinations and of required medical surveillance shall be maintained for the period of employment. The medical representatives of the Secretary of Health, Education, and Welfare, of the Secretary of Labor, of the employer, and of the employee shall have access to all medical records. Section 3 -Labeling (Posting) (a) Containers of anhydrous ammonia shall be marked in accordance with 29 CFR 1910.111 as amended and shall bear the following label in Form 0 -> :A Rev. Mb > 7*# CRITERIA DOCUMENT: RECOMMENDATIONS FOR AN OCCUPATIONAL EXPOSURE STANDARD FOR AMMONIA

# Table of Contents
In addition to the respiratory protection specified in Table 1-1, personnel required to enter atmospheric ammonia concentrations likely to be more than 10,000 ppm shall wear, under an impervious full body suit, a self-contained breathing apparatus with a positive pressure in a full facepiece or a combination supplied air impervious suit, continuous flow type, with auxiliary self-contained air supply. When the worker is using the impervious suit over a self-contained breathing apparatus, stay time in the area shall be limited with due consideration to the heat stress factors involved.
(3) The employer shall supply and maintain all protective clothing in a clean, sanitary, and workable condition.

# (b) Respiratory Protection
The employer shall provide appropriate respirators and ensure proper use when a variance has been granted under the provisions of the Occupa tional Safety and Health Act to allow respirators as a means of control of exposure in routine operations, while the application for variance is pending, or whenever atmospheric concentrations of ammonia exceed 50 ppm, eg, for nonroutine operations, for occasional brief concentrations above the ceiling, cr for emergencies. For these instances a variance is not required, but the requirements set forth below continue to apply.
Appropriate respirators as described in Table 1-1 shall only be used pursuant to the following requirements:
(   First aid procedures will be included, with emphasis on the importance of prompt, copious irrigation of the eyes despite the initial lack of pain.
The information shall be posted in the work area, and kept on file, readily accessible to the worker at all places of employment where ammonia is involved in unit processes and operations, or is released as a product, byproduct, or contaminant.
A continuing educational program shall be instituted to ensure that all workers have current knowledge of job hazards, first aid procedures, proper maintenance procedures and cleanup methods, and that they know how to correctly use respiratory protective equipment and protective clothing.

# Retention of this information by workers in areas required

# Effects on Humans
Ammonium ions are produced in the body as a protein metabolite.  Ammonium ions produced by deamination are rapidly converted in the liver into relatively harmless urea and excreted by the kidney or are used to make new amino acids. Ammonium ions are also produced in the kidney, conserving fixed base, thus maintaining electrolyte balance.

# A. Odor Threshold
Available odor threshold data show a wide variation. Fieldner et al in 1921  reported a threshold of 50 ppm in human exposure experiments.
Smyth  found that 1 ppm was detected and identified by 10 subjects.   The lower concentrations were found at the beginning of the growing period for broiler production, and the higher concentrations at the end when the chickens were caught and the chicken houses were cleaned.

# Details of these experiments
Ventilation intakes near the ceiling of chicken production buildings did not control the ammonia which was produced near the floor. Recommended remedial measures included complete redesign of chicken production facilities, with interim relocation of ventilation intakes to floor level.  concluded that 300-500 ppm, following a period of adaptation, could be tolerated for a prolonged period without harm, and further, that concentrations of 1,000-2,000 ppm were safe for short periods. Lehmann recommended that prolonged exposure to concentrations over 500 ppm should definitely not be allowed. Ammonia concentrations of 70-110 ppm in a gas works were said to be at the threshold of irritation.  September 1973] exposures suggest that one can quickly become accustomed to concentrations of ammonia that at first had been disagreeable.
Although the nasal dryness reported at 50 ppm during a 5-minute exposure  might become irritating after extended exposure, the con centration of ammonia inhaled appears to be the more important factor, the irritating or annoying effects being more dependent upon concentration than length of exposure. For this reason, a standard expressed as a timeweighted average is inappropriate since it would permit fluctuations to concentrations considerably higher than 50 ppm. Therefore, in order to minimize the discomfort felt by some unacclimatized individuals, to

# H. Fire and explosion hazards
While not considered to be a serious fire or explosion hazard,