Mixture Exposure Index
Calculate the combined exposure index to a mixture of chemical agents by the additivity rule, I = (C₁ ÷ TLV₁) + (C₂ ÷ TLV₂), summing the ratio of measured concentration to tolerance limit (TLV) for each substance. The dimensionless result assesses the joint effect of contaminants acting on the same target organ: if the sum exceeds 1, the combined exposure surpasses the limit, even if no single substance is above its own. It is the ACGIH and NR-15 criterion for mixtures with additive effects. Enter the concentrations and tolerance limits of two substances.
Resultado
—
Índice de exposição de mistura
Trabalhadores raramente são expostos a um único agente químico — o ar costuma conter uma mistura de vapores, gases e poeiras. Quando essas substâncias atuam sobre o mesmo órgão-alvo ou pelo mesmo mecanismo (por exemplo, vários solventes que afetam o sistema nervoso), seus efeitos se somam — e avaliar cada uma isoladamente subestima o risco. A regra da aditividade da ACGIH e da NR-15 trata isso com o índice de exposição combinada: I = (C₁ ÷ TLV₁) + (C₂ ÷ TLV₂) + …, somando, para cada substância, a razão entre a concentração medida (C) e o seu limite de tolerância (TLV — Threshold Limit Value, a concentração considerada segura). Cada termo é a 'fração do limite' que aquele agente consome. O critério é claro: se a soma I ≤ 1, a exposição combinada é aceitável; se I > 1, a mistura ultrapassa o limite e há risco, mesmo que nenhuma substância isolada esteja acima do seu próprio TLV. Por exemplo, duas substâncias cada uma a 60% do seu limite (0,6 + 0,6 = 1,2) configuram exposição excessiva juntas. (A aditividade só vale para efeitos sobre o mesmo alvo; para órgãos-alvo independentes, avalia-se cada agente separadamente.) Este índice é fundamental na higiene ocupacional de indústrias químicas, gráficas, de tintas e laboratórios. Informe as concentrações e os limites de tolerância das duas substâncias.
Related Tools
Well Productivity Index
Compute an oil well's productivity index (PI), PI = Q/(Pr − Pwf), the ratio of the produced rate to the pressure differential (drawdown) between the reservoir (Pr) and the bottomhole (Pwf). It measures how easily the well produces: a high PI indicates good permeability and reservoir connection. It is the basis of lift design and production forecasting. Enter the rate and the reservoir and bottomhole pressures.
Soil Group Index (HRB/AASHTO)
Computes the group index of the HRB/AASHTO M 145 classification, the number in parentheses that follows the soil symbol in a soil report: GI = 0.2a + 0.005ac + 0.01bd, where a and b come from the percentage passing the No. 200 sieve and c and d come from the liquid limit and the plasticity index. Each term is truncated — a and b from 0 to 40, c and d from 0 to 20 — and the result is rounded to an integer and never negative, which makes the index range from 0 to 20. The higher the group index, the worse the soil as a subgrade: 0 points to clean, well behaved granular material, values above 12 point to plastic clay that only works once replaced or stabilised, and this is the number that feeds the pavement thickness charts. The complete formula with both terms was adopted; for subgroups A-2-6 and A-2-7 the standard calls for the 0.01bd term alone, and the result is the same: every A-2 soil has at most 35% passing the No. 200 sieve, which is exactly where the a term goes to zero, so the first two terms drop out on their own. Enter the percentage passing the No. 200 sieve, the liquid limit and the plasticity index.
Silt Density Index (SDI)
Computes the silt density index of ASTM D4189, the test that measures the fouling potential of the feed water of a reverse osmosis membrane: the sample is filtered through a 0.45 µm membrane at 207 kPa, the time to collect 500 mL is measured at the start and again at the end of the test, and the index is the percentage of flow loss divided by the duration. The expression is SDI = (1 − initial time ÷ final time) × 100 ÷ duration, and the number tells how much the filter plugged per minute of test: membrane makers usually require under 5 for a spiral wound element and under 3 for extended warranty, and water above that forces stronger coagulation or filtration upstream. The test is only valid if the flow loss stays below 75%; if the filter plugs before that, run it again with a shorter duration. The duration was adopted as an input instead of fixing 15 minutes, the standard value, precisely because poor water demands repeating at 10 or 5 minutes — results from different durations are not comparable, which is why the value is recorded as SDI₁₅, SDI₁₀ or SDI₅. Enter the initial time, the final time and the test duration.
Temperature-Humidity Index (THI) for Cattle
Calculates the temperature-humidity index (THI) used to gauge heat stress in cattle, in the metric form of the 1971 NRC formula, from air temperature and relative humidity. Below 72 the animal is comfortable; 72 to 78 is alert, 79 to 88 is danger and above 88 is emergency. Enter temperature and relative humidity.
Normalized Exposure Level (NEN)
Calculate the 8-hour normalized exposure level (NEN), NEN = NE + 10·log₁₀(t ÷ 480), from the measured exposure level NE (dB(A)) and the actual exposure time t (minutes). The result, in dB(A), converts an exposure of any duration into the equivalent level that would produce the same dose over a standard 8-hour (480 min) shift, allowing direct comparison with the tolerance limit and action level. It is the quantity used by occupational hygiene standards to assess continuous or intermittent noise. Enter the measured level and the exposure time.
BMI Calculator
Calculate your Body Mass Index (BMI) and find your classification according to WHO. Enter weight and height for an instant result.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.