Air Quality Assessment Report for an Industrial Vacant Warehouse

Introduction

The facility was formerly used for manufacturing and presents a deteriorated, open structure, potentially allowing dust and pollutant infiltration. Assessment objectives focused on regulatory compliance, health risk identification, and actionable improvements for occupant safety.

Three AirVue sensors were deployed for seven days to establish whether the building could be reoccupied without remediation.

Background and regulatory context

• EPA NAAQS PM2.5. 35 µg/m³ (24-hour average), 12 µg/m³ (annual average)
• WHO guidelines PM2.5. 15 µg/m³ (24-hour), 5 µg/m³ (annual)
• CO₂ benchmarks, good below 800 ppm, acceptable 800–1,000 ppm, poor above 1,000 ppm
• NOx index, low 0–50, moderate 50–100, high 100–200, very high above 200
• VOC index, low 0–50, moderate 50–200, high 200–400, very high above 500

Methodology

The AirVue monitoring system captured PM mass and number concentrations, CO₂ levels, NOx and VOC indices, atmospheric pressure, altitude, temperature and relative humidity.

Particulate matter was resolved into size bins. PM 0–1 µm, PM 1–2.5 µm, PM 2.5–4 µm and PM 4–10 µm, which is what makes the fine-fraction finding below possible. Sensors were calibrated per manufacturer specifications and data were validated for consistency.

Results: particulate matter

• Daily PM2.5 range. 9.5 to 15.0 µg/m³
• Weekly average PM2.5. 11.5 µg/m³, exceeding the WHO annual guideline of 5 µg/m³
• PM10 range. 14.5 to 20.0 µg/m³
• Peak event, 11 February, maximum PM2.5 of 20.97 µg/m³ and maximum PM10 of 27.72 µg/m³
• Fine particles (PM 0–1 µm and PM 1–2.5 µm) composed approximately 75% of PM2.5 mass

Results: carbon dioxide

Daily averages ranged from 700 to 750 ppm, within the good range below 800 ppm. A single exceedance on 11 February reached 1,088 ppm, classified as poor. Levels stabilised after that date.

Results: nitrogen oxides

Daily average NOx index ranged from 135 to 464 and sat frequently within the high band of 100–200 or above it. A spike on 17 February reached an index of 465, classified very high, and coincided with elevated particulate levels, a combination consistent with a combustion source rather than general infiltration.

Results: volatile organic compounds

Daily averages ranged from 102 to 209, classified moderate. A peak on 11 February reached 310, entering the high band of 200–400. The lowest day was 17 February with an average of 111 and a maximum of 154. Potential sources include benzene, toluene, formaldehyde and related compounds associated with prior manufacturing use.

Health risk assessment

Fine particles pose significant health risks including respiratory conditions such as asthma and bronchitis, cardiovascular events including heart attack and stroke, and premature mortality, the WHO attributes 4.2 million deaths annually to PM2.5 exposure.

CO₂ above 1,000 ppm can cause discomfort and reduced cognitive performance, though the single exceedance here was brief. High NOx causes respiratory irritation, and VOCs at elevated concentrations produce irritation and headaches with long-term carcinogenic risk.

Conclusions

The assessment confirms generally good to moderate air quality with notable concerns. PM2.5 levels approach regulatory thresholds and are driven by the fine fraction. CO₂ was mostly good with a brief poor exceedance. NOx was frequently high with a very high spike. VOCs were moderate with a high exceedance. Health risks from fine particles and NOx require immediate attention.

Recommendations

• Install HEPA filtration to reduce PM2.5
• Enhance ventilation to prevent CO₂ and NOx buildup
• Investigate NOx sources behind the 17 February spike
• Improve dust control to minimise PM infiltration through the open structure
• Investigate VOC sources behind the 11 February spike
• Maintain regular sensor calibration
• Continue monitoring with periodic assessments