# Nitrogen Dioxide

Nitrogen Oxide ( $NO$ ) and Nitrogen Dioxide ( $NO_2$ ) are often referred as ( $NO_x$ ). The most widely spread source of $NO_x$ pollution are internal combustion engines. NOx generation in engines is mostly influenced by the combustions temperature and duration of the gas being at high temperature. Greater the combustion temperature and duration - greater the NOx generation. Engine makers are obligated to implement $NO_x$ reduction design. In order to minimize $NO_x$ emission and other pollutants emission, it is important to keep engine tuned up to makers standards and use original parts for replacement during repairs and overhauls.

The fossil-fueled household appliances used for cooking and heating are the other source of Nitrogen Dioxide.

$NO_2$ hits the respiratory system. May cause illnesses or damage of lung and breathing passages. When combined with water in the atmosphere, Nitrogen Dioxide forms Nitric acid and contributes to acid rains.

## Regulatory levels

### Regulations for industrial environments

• OSHA:
• 5 ppm - highest permissible concentration
• MAK
• 5 ppm - highest average concentration for any 8-hours period
• 10 ppm - highest average concentration for any 5-min period
• GOST 12.1.005-88 Occupational safety standards system. General sanitary requirements for working zone air
• 2 $\mu g/m^3$ - highest permissible concentration
• 5 $\mu g/m^3$ - for all $NO_x$ combined - highest permissible concentration

### Outdoor air regulatory levels

• U.S. EPA
• 100 ppb (188 $\mu g/m^3$) - highest average concentration for any 1-year period
• 0.053 ppm - highest average concentration for any 1-year period
• California
• 0.18 ppm (399 $\mu g/m^3$) - highest average concentration for any 1-year period
• 0.03 ppm (57 $\mu g/m^3$) - highest average concentration for any 1-year period
• Japan
• 0.06 ppm - highest average concentration for any 24-hours period

## Reference levels

### Reference levels for industrial environments

• NIOSH:
• 1 ppm - highest average concentration for any 5-min period
• 200 ppm - maximum exposure
• ACGIH
• 3 ppm - highest average concentration for any 8-hours period
• 5 ppm - highest average concentration for any 15-min period

### General reference levels

• ASHRAE
• 100 $\mu g/m^3$ - average exposure for 1 year
• 470 $\mu g/m^3$ - maximum 24-hours average
• WHO:
• 0.02 ppm - highest average concentration for any 1-rear period
• 0.1 ppm - highest average concentration for any 1-hour period